Ventilation System 

Effectiveness and Tested 

Indoor Air Quality Impacts

Armin Rudd and Daniel Bergey

Building Science Corporation

February 2014
NOTICE

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iii

Ventilation System Effectiveness and 

Tested Indoor Air Quality Impacts

Prepared for:

The National Renewable Energy Laboratory

On behalf of the U.S. Department of Energy’s Building America Program

Office of Energy Efficiency and Renewable Energy

15013 Denver West Parkway

Golden, CO 80401

NREL Contract No. DE-AC36-08GO28308

Prepared by: 

Armin Rudd and Daniel Bergey

Building Science Corporation

30 Forest Street

Somerville, MA 02143

NREL Technical Monitor: Cheryn Metzger

Prepared under Subcontract No. KNDJ-0-40337-03

February 2014
iv

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v

Contents

List of Figures ..........................................................................................................................vi

List of Tables..........................................................................................................................viii

Definitions ................................................................................................................................ix

Acknowledgments ....................................................................................................................x

Executive Summary.................................................................................................................xi

1 Problem Statement..............................................................................................................1

1.1 Introduction...................................................................................................................................... 1

1.2 Background...................................................................................................................................... 1

1.2.1 Research Questions............................................................................................................. 3

1.3 Relevance to Building America’s Goals.......................................................................................... 3

1.4 Cost Effectiveness............................................................................................................................ 4

1.5 Tradeoffs and Other Benefits........................................................................................................... 8

2 Previous Research..............................................................................................................9

3 Test and Analysis Method ................................................................................................10

3.1 Description of the Test Houses...................................................................................................... 10

3.2 HVAC System Modifications and Pretesting ................................................................................ 13

3.3 Testing Approach........................................................................................................................... 15

3.3.1 Baseline Test..................................................................................................................... 18

3.3.2 Exhaust Test...................................................................................................................... 18

3.3.3 Exhaust With Mixing Test................................................................................................ 18

3.3.4 Central Fan Integrated Supply Test .................................................................................. 19

3.3.5 Energy Recovery Ventilator Test...................................................................................... 19

3.4 Building Enclosure, Central Air Distribution System, and Ventilation Systems Characterization19

3.5 Per-Fluorocarbon Tracer Gas Testing............................................................................................ 19

3.6 Airborne Particulate Sampling....................................................................................................... 22

3.7 Volatile Organic Compound Sampling.......................................................................................... 24

3.8 Formaldehyde Sampling ................................................................................................................ 25

4 Discussion of Results.......................................................................................................26

4.1 Building Air Leakage Characterization ......................................................................................... 26

4.1.1 Fan Pressurization Tests ................................................................................................... 26

4.2 HVAC Characterization................................................................................................................. 26

4.3 Per-Fluorocarbon Tracer Gas testing............................................................................................. 29

4.3.1 Zone Air Change Rates..................................................................................................... 29

4.3.2 Interzonal Airflows........................................................................................................... 33

4.4 Airborne Particulate Sampling....................................................................................................... 42

4.5 Formaldehyde Sampling ................................................................................................................ 53

4.6 Volatile Organic Compound Sampling.......................................................................................... 56

5 Summary of Results..........................................................................................................67

6 Author Recommendations................................................................................................70

6.1 Relevant Issues With ASHRAE Standard 62.2 ............................................................................. 70

6.1.1 Source of Outside Air ....................................................................................................... 70

6.1.2 Ventilation Effectiveness.................................................................................................. 71

6.2 Recommendations for Ventilation Rates....................................................................................... 72

References ..............................................................................................................................76

Appendix A: Listing of All Top 20 Volatile Organic Compounds Found, and Their 

Functional Descriptions....................................................................................................78

Appendix B: Preliminary CONTAM Model.............................................................................82
vi

List of Figures

Figure 1. Energy savings and costs: vented attic, 5% duct leakage ..................................................... 7

Figure 2. Energy savings and costs: vented attic, no duct leakage...................................................... 7

Figure 3. Energy savings and costs: unvented attic, no duct leakage ................................................. 8

Figure 5. Location and directions to the test homes at University of Texas-Tyler............................ 10

Figure 5. House 1 vented attic (left) and House 2 unvented attic (right)............................................. 11

Figure 6. Exterior photos of the test homes at the UT-Tyler; House 1 has the darker roof ............. 11

Figure 7. Energy recovery ventilator (ERV) installed in House 1 to match that of House 2 ............. 12

Figure 9. Wye'd outside air duct, airflow stations, and inline fan for retrofitting a central fan 

integrated supply (CFIS) ventilation system in each attic (left); setting the CFIS airflow rate 

with Iris damper airflow station (top); fan timer and relay arrangement (bottom) ...................... 13

Figure 9. Test house floor plan................................................................................................................ 14

Figure 10. House 1 temperature and RH in indoor zones and outdoors during each test period.... 16

Figure 11. House 2 temperature and RH in indoor zones and outdoors during each test period.... 17

Figure 12. Wind speed during each of the test periods; green and red markers indicate start and 

stop of the 12-hour sampling periods .............................................................................................. 17

Figure 13. House 2 main zone with PFT source tripod on left and sampling station tripod on right21

Figure 14. PFT source (left) and primary and backup CATS (right) .................................................... 22

Figure 15. Cumulative particle counts for six particle sizes during the baseline test in House 2, 

main zone; results show impact on large particle counts due to human disturbance 1.5 hours 

before end of sampling period.......................................................................................................... 23

Figure 16. Test fixture tripod holding (left to right in photos) HCHO sample pump, temperature and 

relative humidity data logger, PFT sample tubes (CATS), airborne particulate counter, and 

VOC sampling pump .......................................................................................................................... 23

Figure 17. VOC sampling pump and solid sorbent sample tube; airborne particulate counter on 

top of sampling fixture....................................................................................................................... 24

Figure 18. Air change rates in the living space zones for House 1, for the baseline test and four 

different ventilation systems............................................................................................................. 30

Figure 19. Measured air change rates in the garage and attic zones for House 1, for different 

ventilation systems ............................................................................................................................ 31

Figure 20. Air change rates in the living space zones for House 2 (unvented attic), for the baseline 

test and four different ventilation systems, showing the same trends as House 1 .................... 32

Figure 21. Measured air change rates in the garage and unvented attic zones for House 2, for the 

baseline test and four different ventilation systems ...................................................................... 33

Figure 22. Airflow from garage to living area zones in House 1, for the baseline test and four 

different ventilation systems............................................................................................................. 34

Figure 23. Airflow from garage to living area zones in House 2, for the baseline test and four 

different ventilation systems, showing the same trends as House 1 ........................................... 35

Figure 24. Airflow from attic to living area zones in House 1, for the baseline test and four 

different ventilation systems............................................................................................................. 36

Figure 25. Airflow from attic to living area zones in House 2, for the baseline test and four 

different ventilation systems............................................................................................................. 37

Figure 26. Backup CATS analyzed for QA/QC check; House 2, Test 2 (exhaust) .............................. 38

Figure 27. House 1 interzonal airflows for living space zones............................................................. 39

Figure 28. House 1 reverse direction interzonal airflows for living space zones .............................. 40

Figure 29. House 2 interzonal airflows for living space zones............................................................. 41

Figure 30. House 2 reverse direction interzonal airflows for living space zones .............................. 42

Figure 31. Cumulative particle counts for six particle sizes (0.3–10 micrometer) for the House1 

main and master zones...................................................................................................................... 45

Figure 32. Cumulative particle counts for six particle sizes (0.3–10 micrometer) for the House 2 

main and master zones...................................................................................................................... 47

Figure 33. Cumulative particle counts for six particle sizes (0.3–10 micrometer) for the attic and 

garage zones for House 1 and House 2 ........................................................................................... 51

Figure 34. Cumulative particle counts for six particle sizes (0.3–10 micrometer) sampled outside 
vii

on the first and last test days (test day 1 and test day 6) .............................................................. 52

Figure 35. Cumulative particle counts for six particle sizes (0.3–10.0 micron) for simultaneous 

measurements made outside and inside during the H2 baseline test.......................................... 53

Figure 36. HCHO concentration measured in the main and master zones of House 1 and House 2 

during the baseline test and four ventilation system tests............................................................ 55

Figure 37. Attic and garage HCHO concentrations for both houses................................................... 55

Figure 38. Concentrations of the top 11 VOCs found in the main zone of House 1, for the baseline 

test and four different ventilation systems...................................................................................... 57

Figure 39. Concentrations of the top 11 VOCs found in the master zone of House 1, for the 

baseline test and four different ventilation systems ...................................................................... 57

Figure 40. Concentrations of the top 10 VOCs found in the main zone of House 2, for the baseline 

test and four different ventilation systems...................................................................................... 58

Figure 41. Concentrations of the top 10 VOCs found in House 2 master zone, for the baseline test 

and four different ventilation systems ............................................................................................. 58

Figure 42. VOCs found in the attics of House 1 and House 2 .............................................................. 63

Figure 43. VOCs found in the garages of House 1 and House 2.......................................................... 66

Figure 44 CONTAM Model of House 1 .................................................................................................... 86

Figure 45. CONTAM Model of House 2 ................................................................................................... 86

Unless otherwise noted, all figures were created by BSC.
viii

List of Tables

Table 1. Calculations Showing That ASHRAE Standard 62.2-2013 Ventilation Fan Airflow Rates Are 

About 40% Higher Than ASHRAE Standard 62.2-2010, Averaged Over a Range of Climates, 

Building Archetypes, and Building Airtightness............................................................................... 2

Table 2. BEopt Simulations of the UT-Tyler Houses With Unvented Attic and Vented Attic, Showing 

Energy Consumption by End Use for Different Ventilation Systems and Ventilation Airflow 

Rates ...................................................................................................................................................... 5

Table 3. Test Number, Name, and Description of the Five Tests Conducted in Each House ........... 16

Table 4. Type and Number of Tracer Gas Sources Used in Each House and Test............................ 20

Table 5. Physical Characteristics of the Test Houses........................................................................... 26

Table 6. Typically Reported Blower Door Test Results For Each Test House ................................... 27

Table 7. Duct Leakage Tests.................................................................................................................... 28

Table 8. Central Air Distribution System (Heat Pump) Cooling Supply Airflows ............................... 28

Table 9. Ventilation System Airflow and Runtime Setup ...................................................................... 28

Table 10. Calculation of Differential Particle Counts Over the Range of 0.3–2.0 Micron; the Percent 

Differences in Differential Counts Are Shown Compared to the Exhaust Ventilation System .. 48

Table 11. Cumulative Particle Counts Measured Outdoors and in the House 1 and House 2 Attics49

Table 12. Cumulative and Differential Particle Counts Measured Outdoors During Baseline Tests 

on the First and Last Test Days ........................................................................................................ 50

Table 13. HCHO Concentrations in House 1 and House 2, for the Baseline Test and Four Different 

Ventilation Systems ........................................................................................................................... 54

Table 14. TVOC by House, Zone, and Ventilation System.................................................................... 59

Table 15. TVOC Measurements in the Attic and Garage Zones of Both Houses ............................... 60

Table 16. VOCs Found in Both Attics, Sorted by High to Low Concentration in the House 2 

Unvented Attic .................................................................................................................................... 61

Table 17. VOCs Found in Both Garages, Sorted by Highest to Lowest in the House 1 Garage....... 64

Table 18. Recommended System Factors To Reduce Ventilation Fan Airflow Rates Relative to 

ASHRAE Standard 62.2-2013............................................................................................................. 73

Table 19. Numerical Basis for the System Factors Shown in Table 18, Given as Percent Airflow 

Rate Reduction for Each System Factor Category ......................................................................... 75

Table 20. Listing of All Top 20 Volatile Organic Compounds Found, and Their Functional 

Descriptions........................................................................................................................................ 79

Table 21. House 1 Guarded and Unguarded Fan Pressurization Test Results .................................. 83

Table 22. House 2 (Unvented Attic) Guarded and Unguarded Fan Pressurization Test Results ..... 84

Table 23. House 1 CONTAM Model Inputs.............................................................................................. 85

Table 24. House 2 CONTAM Model Inputs.............................................................................................. 86

Unless otherwise noted, all tables were created by BSC.
ix

Definitions

ach Air changes per hour

ach50 Air changes per hour at 50 Pascal pressure differential

AIMS Air Infiltration Measurement System

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning 

Engineers

ASTM American Society for Testing And Materials

BeOptTM Building Energy Optimization Program

BNL Brookhaven National Laboratory

BSC Building Science Corporation

CATS Capillary Adsorption Tube Sampler

CFIS Central fan integrated supply ventilation

CFM 50 Cubic feet per minute at 50 Pascal test pressure differential

CONTAM Contaminant transport computer program

DOE U.S. Department of Energy

EPA U.S. Environmental Protection Agency

ERV Energy recovery ventilator

HCHO Formaldehyde

HUD U.S. Department of Housing and Urban Development

HVAC Heating, ventilation, and air conditioning

IMC International Mechanical Code

MBC Minnesota Building Code

MERV Minimum Efficiency Rating Value

MPR Microparticle Performance Rating

NBC National Building Code of Canada

NREL National Renewable Energy Laboratory

Pa Pascal; SI unit of pressure (equivalent to one newton/m

2

)

PFT Per-Fluorocarbon Tracer

QA Quality assurance

QC Quality control

RH Relative humidity

UL-AQS Underwriters Laboratory - Air Quality Sciences Division

UT-Tyler University of Texas-Tyler

WAVIAQ Washington State Ventilation and Indoor Air Quality Code
x

Acknowledgments

The Texas Allergy, Indoor Environment, & Energy Institute at The University of Texas-Tyler, 

under direction of Roy Crawford, Ph.D. and John Vasselli, provided the two lab houses for this 

research. Dr. Crawford also participated in our efforts.

Appreciation is also extended to Fluke Corporation and Underwriters Laboratories Air Quality 

Sciences, Inc. for assisting financially with the airborne particle counting and volatile organic 

compound (VOC)/formaldehyde phases of the project. Thanks to Terry Sullivan at Brookhaven 

National Laboratory for his technical guidance with the Passive Fluorocarbon Tracer testing, and 

to Colin Olson of the Energy Conservatory for his consultations concerning the multizone fan 

pressurization testing.
xi

Executive Summary

Airtightness of new homes is critical to achieving low-energy consumption, healthy and 

comfortable spaces, and durability. Airtight homes require rational and predictable ventilation. A 

key gap and area of ongoing research is to allow credit for better performing ventilation systems.

Building on previous research dealing with ventilation air distribution, this study added new 

elements of ventilation effectiveness research, accounting for source of outside air, particle 

contaminants, and VOC contaminants.

The study focused on the in-situ impacts of various ventilation systems, including the impacts of 

differing sources of outside air and the spatial distribution and filtration of ventilation air. The 

project involved testing two unoccupied, single-family, detached homes in Tyler, Texas that 

were constructed as lab homes at the University of Texas-Tyler.1 These twin lab homes offered a 

unique opportunity for the direct comparison of nearly identical homes except for one having a 

vented attic and the other having an unvented attic assembly (also known as sealed cathedralized 

attic).

Exhaust ventilation testing showed lower uniformity of outdoor air exchange rate between living 

space zones, and higher concentrations of particulates, formaldehyde, and other Top 20 VOCs

than did the supply and balanced ventilation systems. This showed that single-point exhaust 

ventilation was inferior as a whole-house ventilation strategy because the source of outside air 

was not directly from outside (much of it came from the attic), the ventilation air was not 

distributed, and no provision existed for air filtration. Indoor air recirculation by a central air 

distribution system can help improve the exhaust ventilation system by way of air mixing and 

filtration. In contrast, the supply and balanced ventilation systems showed that there is a 

significant benefit to drawing outside air from a known outside location, and filtering and fully 

distributing that air.

The central fan integrated supply (CFIS) ventilation system showed an 85% and 73% reduction 

in 0.3–2.0 micron particles for House 1 and House 2, respectively, attributable to recirculation air 

filtration by operation of the central air distribution system.

Total volatile organic compound (TVOC) data showed that, compared to the exhaust system, the 

CFIS and energy recovery ventilation systems reduced TVOCs by 47% and 57%, respectively, 

averaged between the two houses. Compared to the baseline tests, the exhaust system increased 

TVOCs by 37% in the House 1 main zone, and increased TVOCs by 18% in the House 2 master 

zone. This highlights that the unknown air path, or source of outside air, for the exhaust 

ventilation system can cause indoor air to be more contaminated depending on what 

contaminants are picked up on the way in.

The author of this report believes that these new data support ventilation rate credits for better 

performing ventilation systems. The recommendations in this report for the ASHRAE 62.2 

committee intend to provide specific guidance for understanding whole-building ventilation 

system effectiveness, which is critical to promoting the best low energy and high value 

ventilation solutions.

 1 Learn more at www.UT Tyler.edu/TxAIRE/Technology/Houses
xii

Ventilation system factors recommended by the author, based on the results of this study could 

be applied to ASHRAE 62.2 standards to account for ventilation system attributes that improve 

the system’s performance. Application of these recommendations would yield energy savings 

and reduced moisture control risk in humid climates, without compromising indoor air quality 

relative to the exhaust systems (currently allowed by ASHRAE Standard 62.2-2013). Such 

ventilation rate credits would also benefit the U.S. Environmental Protection Agency Indoor Air 

Program and the U.S. Department of Energy Challenge Home.
1

1 Problem Statement

1.1 Introduction

This study focuses on the in-situ impacts of various ventilation systems, including the impacts of 

differing sources of outside air and the spatial distribution and filtration of ventilation air. The 

project involved testing two unoccupied, single-family, detached homes in Tyler, Texas that 

were constructed as lab homes at the University of Texas-Tyler (UT-Tyler).

2 These twin lab 

homes offered a unique opportunity for the direct comparison of nearly identical homes except 

for one having a vented attic and the other having an unvented attic assembly (also known as 

sealed cathedralized attic).

1.2 Background

The residential building sector consumes approximately 21% of the primary energy used in the 

United States. Energy consumption due to ventilation needs is increasingly becoming a high 

percentage of total space conditioning energy consumption. Accounting for better performing 

ventilation systems is a reasonable step in the effort to reduce energy consumption without 

compromising indoor air quality, comfort, or durability.

Airtightness of new homes is critical to achieving low energy consumption, healthy spaces, and 

durability. Airtight homes require rational and predictable ventilation. A key area of ongoing 

research is the ventilation airflow rates of the ASHRAE Standard 62.2-2013, having about 40% 

higher airflow requirement relative to ASHRAE Standard 62.2-2010; see ). Identifying methods 

to reduce energy consumption, improve humidity control performance, and improve indoor air 

quality would benefit the U.S. Environmental Protection Agency (EPA) Indoor Air Program 

required by the U.S. Department of Energy (DOE) Challenge Home. This author believes that 

research should be conducted into methods that include considerations for: 

• Accounting for the quality of the source of outside air for different ventilation systems 

types.

• Accounting for ventilation air distribution effectiveness.

• Managing hazardous indoor air pollutants in ways other than air change.

 2 Learn more at www.UT Tyler.edu/TxAIRE/Technology/Houses
2

Table 1. Calculations Showing That ASHRAE Standard 62.2-2013 Ventilation Fan Airflow Rates Are About 40% Higher Than ASHRAE 

Standard 62.2-2010, Averaged Over a Range of Climates, Building Archetypes, and Building Airtightness

Climate Zone Location ASHRAE 

WSF*

Two-Story, 62.2-2010, cfm 54 One-Story, 62.2-2010, cfm 54

3.0, ach50 1.5, ach50 3.0, ach50 1.5, ach50

62.2-

2013 

Fan 

cfm

Diff. 

From 

62.2-2010 

Fan cfm

(%)

62.2-

2013 

Fan cfm

Diff. 

From 

62.2-

2010 

Fan cfm

(%)

62.2-

2013 Fan 

cfm

Diff. 

From 

62.2-2010 

Fan cfm

(%)

62.2-

2013 

Fan 

cfm

Diff. 

From 

62.2-2010 

Fan cfm

(%)

Warm-Humid Orlando 0.39 73 35 88 62 71 42 81 61

Warm-Humid Houston 0.40 72 34 87 61 71 41 80 61

Warm-Humid Charleston 0.43 70 30 86 59 69 38 80 59

Mixed-Humid Baltimore 0.50 65 20 83 55 66 31 78 56

Mixed-Humid Kansas City 0.60 58 7 80 48 61 22 75 51

Mixed-Humid Charlotte 0.43 70 30 86 59 69 38 80 59

Cold-Humid Minneapolis 0.63 55 2 79 46 59 19 75 49

Cold-Humid Chicago 0.60 58 7 80 48 61 22 75 51

Dry Phoenix 0.43 70 30 86 59 69 38 80 59

Dry Denver 0.61 57 5 79 47 60 21 75 50

Marine Los Angeles 0.42 71 31 86 60 70 39 80 60

Marine Seattle 0.56 61 12 81 50 63 26 76 53

Average of Climates 65 20 83 55 66 31 78 56

Average of Climate, Archetype, and 

Airtightness 73 40

* ASHRAE 62.2 Weather and Shielding Factor per ASHRAE 62.202013
3

1.2.1 Research Questions

The research presented in this report is intended to help develop a better understanding of wholebuilding ventilation system effectiveness and distribution in low energy homes, which is critical 

to promoting the best low-energy and high-value ventilation solutions. Building Science 

Corporation (BSC) seeks to address the following research questions:

1. Do different whole-building ventilation systems perform significantly differently in terms 

of their ability to deliver uncontaminated ventilation air to the occupants?

2. What measurements and testing protocols are needed to appropriately account for the 

source of outside air relevant to occupant exposure to chemical and particulate 

contaminants and their expected satisfaction with indoor air in residential environments?

3. What is the overall indoor air quality impact of operating an exhaust whole-building 

ventilation system versus supply and balanced ventilation?

4. For whole-building ventilation systems that do not draw outside air directly from a 

known fresh air source, how much of the ventilation air is drawn through potentially 

contaminated adjacent spaces such as garages and vented attics?

5. What is the impact of drawing outdoor air through the building enclosure and adjacent 

unoccupied spaces on the level of particulate contaminants within the conditioned space?

6. What is the level of chemical contaminants within the conditioned space and adjacent 

spaces, and the impact of drawing outdoor air through the building enclosure and 

adjacent unoccupied spaces? What is the impact of drawing outdoor air through the 

building enclosure and adjacent unoccupied spaces on the level of chemical contaminants 

within the conditioned space?

1.3 Relevance to Building America’s Goals

Overall, the goal of the DOE Building America program is to “reduce home energy use by 30%–

50% (compared to 2009 energy codes for new homes and pre-retrofit energy use for existing 

homes).” To this end, we conduct research to “develop market-ready energy solutions that 

improve efficiency of new and existing homes in each U.S. climate zone, while increasing 

comfort, safety, and durability.”3

The combination of air-sealed building enclosures and controlled mechanical ventilation is an 

effective means to reduce energy consumption while providing improved indoor air quality and 

comfort in residential buildings. The results of this research project will further inform the 

residential building community on how effective different whole-building ventilation systems are 

in meeting these necessary goals. The results presented here provide new data on in-field 

performance of mechanical ventilations systems. The data provide further understanding 

regarding whole-building ventilation system effectiveness, including the impacts of ventilation 

air distribution, the source of outside air, and particulate and VOC contaminant levels. This

information is critical for developing strategies to encourage the lowest energy and highest value 

ventilation solutions.

 3 www1.eere.energy.gov/buildings/building_america/program_goals.html
4

1.4 Cost Effectiveness

Ventilation energy consumption is a significant part of the energy consumption and energy cost 

of low energy homes. Understanding whole-building ventilation system performance in low 

energy homes is critical to promoting the highest value ventilation solutions for reducing energy 

consumption while providing good indoor air quality and comfort for the occupants.

Overventilation unnecessarily consumes energy and raises the risk of comfort and indoor air 

quality problems due to elevated indoor humidity in warm-humid climates. Higher performing 

ventilation systems may be able to eliminate unnecessary overventilation, thereby providing 

equal or improved indoor air quality and comfort at lower cost.

The BEoptTM (Building Energy Optimization) software provides capabilities to evaluate 

residential building designs and identify cost-optimal efficiency packages at various levels of 

whole-house energy savings (Christensen et al. 2006). Table 2 shows results from BEopt 

simulations of the 1475 ft2 UT-Tyler houses with an unvented attic and a vented attic. Energy 

consumption is listed by end use for different ventilation systems, and for ventilation airflow 

rates equal to the ASHRAE Standard 62.2-2010 rate and 50% of that for systems that draw the 

outside air from a known fresh air location, filter, and fully distribute that ventilation air to the 

breathing zone of the occupants. Energy cost was calculated at a rate of $0.103/kWh.

BEopt simulations for the UT-Tyler houses projected that ventilation accounts for 4%–6% of 

total energy consumption, and that ventilation accounts for 12%–22% of heating, ventilation, and 

air conditioning (HVAC) energy consumption. Reducing the ASHRAE 62.2-2010 ventilation 

rate by 50% (the basis for this is provided in Section 5) was projected to reduce HVAC energy 

used for conditioning ventilation air by 8% to 10%, and was projected to reduce total energy

consumption by 2% to 3%. With ASHRAE 62.2-2013 ventilation rates being about 40% higher 

than ASHRAE Standard 62.2-2010, if ENERGY STAR® and the DOE Challenge Home 

programs were to reference the 2013 rates, then the savings would be higher.
5

Table 2. BEopt Simulations of the UT-Tyler Houses With Unvented Attic and Vented Attic, Showing 

Energy Consumption by End Use for Different Ventilation Systems and Ventilation Airflow Rates

1—Exhaust 

100% 62.2

2—Supply 

100% 62.2

3—ERV 

100% 62.2

4—Supply 

50% 62.2

5—ERV 

50% 62.2

6—No 

Ventilation

Unvented Attic, No Duct Losses Source Energy Use (MBtu/yr)

Miscellaneous (E) 37.56 37.56 37.56 37.56 37.56 37.56

Ventilation Fan (E) 1.66 1.66 4.97 0.96 2.62 0.25

Large Appliances (E) 20.25 20.25 20.25 20.25 20.25 20.25

Lights (E) 11.42 11.42 11.42 11.42 11.42 11.42

HVAC Fan/Pump (E) 2.81 2.84 2.79 2.69 2.72 2.61

Cooling (E) 16.73 16.79 16.61 16.07 16.18 15.53

Heating (E) 17.76 17.49 17.23 16.35 16.77 15.84

Hot Water (E) 26.05 26.05 26.05 26.05 26.05 26.05

Total 134.25 134.06 136.89 131.36 133.57 129.52

Ventilation % Total 4% 4% 6% 1% 3% 0%

Diff 50% 62.2 Versus 100% 62.2 2% 3%

HVAC Subtotal 38.96 38.78 41.6 36.07 38.29 34.23

Ventilation % HVAC 14% 13% 22% 5% 12% 0%

Diff 50% 62.2 Versus 100% 62.2 8% 10%

Vented Attic, 5% Duct Leakage Source Energy Use (MBtu/yr)

Miscellaneous (E) 37.56 37.56 37.56 37.56 37.56 37.56

Ventilation Fan (E) 1.66 1.66 4.97 0.96 2.62 0.25

Large Appliances (E) 20.25 20.25 20.25 20.25 20.25 20.25

Lights (E) 11.42 11.42 11.42 11.42 11.42 11.42

HVAC Fan/Pump (E) 3.34 3.48 3.27 3.2 3.21 3.08

Cooling (E) 18.47 18.8 18.46 17.98 18.04 17.41

Heating (E) 23.93 24.19 23.13 22.32 22.65 21.54

Hot Water (E) 26.05 26.05 26.05 26.05 26.05 26.05

Total 142.69 143.41 145.12 139.75 141.81 137.56

Ventilation % Total 4% 4% 5% 2% 3% 0%

Diff 50% 62.2 Versus 100% 62.2 3% 2%

HVAC Subtotal 47.4 48.13 49.83 44.46 46.52 42.28

Ventilation % HVAC 12% 14% 18% 5% 10% 0%

Diff 50% 62.2 Versus 100% 62.2 9% 8%
6

Vented Attic, No Duct Losses Source Energy Use (MBtu/yr)

1—Exhaust 

100% 62.2

2—Supply 

100% 62.2

3—ERV 

100% 62.2

4—Supply 

50% 62.2

5—ERV 

50% 62.2

6—No 

Ventilation

Miscellaneous (E) 37.56 37.56 37.56 37.56 37.56 37.56

Ventilation Fan (E) 1.66 1.66 4.97 0.96 2.62 0.25

Large Appliances (E) 20.25 20.25 20.25 20.25 20.25 20.25

Lights (E) 11.42 11.42 11.42 11.42 11.42 11.42

HVAC Fan/Pump (E) 2.5 2.53 2.47 2.37 2.4 2.28

Cooling (E) 13.78 13.88 13.73 13.22 13.32 12.72

Heating (E) 17.52 17.3 16.97 16.07 16.5 15.55

Hot Water (E) 26.05 26.05 26.05 26.05 26.05 26.05

Total 130.75 130.66 133.43 127.9 130.12 126.09

Ventilation % Total 4% 4% 6% 1% 3% 0%

Diff 50% 62.2 Versus 100% 62.2 2% 3%

HVAC Subtotal 35.46 35.37 38.14 32.62 34.84 30.8

Ventilation % HVAC 15% 15% 24% 6% 13% 0%

Diff 50% 62.2 Versus 100% 62.2 9% 11%
7

Figure 1. Energy savings and costs: vented attic, 5% duct leakage

Figure 2. Energy savings and costs: vented attic, no duct leakage

Exhaust 100% 

62.2

Supply 100% 

62.2

ERV 100% 62.2

Supply 50% 

62.2

ERV 50% 62.2

No Ventilation

1100

1150

1200

1250

1300

1350

1400

1450

-2 -1 0 1 2 3 4

Annualized Energy Related Costs [$]

Source Energy Savings [%/yr]

Exhaust 100% 

62.2

Supply 100% 

62.2

ERV 100% 62.2

Supply 50% 

62.2

ERV 50% 62.2

No Ventilation 1100

1150

1200

1250

1300

1350

1400

1450

-3 -2 -1 0 1 2 3 4

Annualized Energy Related Costs [$]

Source Energy Savings [%/yr]
8

Figure 3. Energy savings and costs: unvented attic, no duct leakage

1.5 Tradeoffs and Other Benefits

Overventilation unnecessarily consumes energy and raises the risk of comfort and indoor air 

quality complaint problems due to elevated indoor humidity in warm-humid climates (Rudd and 

Henderson 2007). Higher performing ventilation systems may be able to eliminate unnecessary 

overventilation, thereby providing equal or improved indoor air quality and comfort at lower 

cost.

Exhaust 100% 

62.2

Supply 100% 

62.2

ERV 100% 62.2

Supply 50% 

62.2

ERV 50% 62.2

No Ventilation

1000

1050

1100

1150

1200

1250

1300

1350

1400

1450

-3 -2 -1 0 1 2 3 4

Annualized Energy Related Costs [$]

Source Energy Savings [%/yr]
9

2 Previous Research

Significant work has been done by the BSC and others in the area of ventilation air distribution 

effectiveness under past Building America work, which has been directed toward changes to 

ASHRAE Standard 62.2. Field testing and CONTAM (Walton and Dols 2010) modeling 

associated with that work has shown that ventilation air distribution effectiveness varies widely 

between ventilation systems (Rudd and Lstiburek 2000; Rudd and Lstiburek 2001; Hendron et al. 

2006; Hendron et al. 2007; Rudd and Lstiburek 2008; Townsend et al. 2009a; Townsend et al. 

2009b). This author has found that utilizing high performing systems that draw outside air from a 

known fresh air location, and filter and fully distribute that air to the occupants breathing zone 

(including bedrooms where occupants spend the most continuous time), allows for optimization 

of the ventilation rate to avoid problems of overventilation.
10

3 Test and Analysis Method

3.1 Description of the Test Houses

The project involved testing at two unoccupied, single-family, detached homes in Tyler, Texas

that were constructed as lab homes at UT-Tyler.4 Figure 5 shows the campus location and 

directions to the test homes. The twin lab homes offered a unique opportunity for the direct 

comparison of nearly identical homes except for House 1 having a vented attic (see Figure 5) and 

House 2 having an unvented attic assembly5 (also known as sealed cathedralized attic). House 1 

had 2 × 4 frame walls with netted and blown fiberglass insulation, and loose blown fiberglass 

insulation on the floor of the attic. House 2 had 2 × 6 advanced-framed walls with low-density 

spray foam insulation in the walls and under the attic roof deck. The homes were completely 

finished, with kitchen and bathroom cabinets, but were unfurnished. This allowed an evaluation

focus on the building elements themselves, avoiding conflation with items particular individuals 

bring into their homes (Hodgson et al. 2000). Figure 6 shows exterior views of the test homes.

House 1 has the darker colored roof and House 2 the lighter colored roof. Figure 9 shows the 

House 1 floor plan layout, which applies to both houses since the plans are simply flipped 

(mirrored) with respect to each other.

Figure 4. Location and directions to the test homes at University of Texas-Tyler

 4 Learn more at www.UT Tyler.edu/TxAIRE/Technology/Houses 5 Refer to International Residential Code section R806.4
11

Figure 5. House 1 vented attic (left) and House 2 unvented attic (right)

Figure 6. Exterior photos of the test homes at the UT-Tyler; 

House 1 has the darker roof
12

Zone designations for the testing were as follows:

• Main zone included the kitchen, dining area, living area, foyer, and family bathroom.

• Master zone included the master bedroom, master bathroom, and walk-in closet.

• Front zone was the bedroom on the front side of the house (labeled Bedroom 2 in Figure 

9).

• Middle zone was the bedroom between the master bathroom and the family bathroom 

(labeled Bedroom 3 in Figure 9).

• Attic zone was the vented attic for House 1 (including the vented attic over the garage) 

and the unvented attic for House 2 (the vented attic over the garage for House 2 was 

separate from the unvented attic and the garage but was not monitored as a separate 

zone).

• Garage zone was the two-car garage.

Figure 7. Energy recovery ventilator (ERV) installed in House 1 to match that of House 2
13

Figure 8. Wye'd outside air duct, airflow stations, and inline fan for retrofitting a central fan 

integrated supply (CFIS) ventilation system in each attic (left); setting the CFIS airflow rate with 

Iris damper airflow station (top); fan timer and relay arrangement (bottom)

3.2 HVAC System Modifications and Pretesting

In order to test both houses with the same ventilation systems, the following HVAC system 

modifications were made prior to testing:

• An ERV system was installed in House 1 to be identical to the one installed in House 2 

(see Figure 7).

• Provisions were made with a 6-in. wye fitting and damper arrangement such that the 

outside air duct serving each ERV could be switched to serve as the outside air duct for a 

newly installed CFIS ventilation system. A timer and relay arrangement was installed that 

controlled the central system fan and an inline supply fan to provide the desired supply 

ventilation airflow at the desired fan duty cycle . The outside airflow was set by a 

balancing damper and calibrated flow measuring station (see Figure 9).

• The same timer that controlled the central fan for the CFIS system was used to control the 

central fan for the exhaust with mixing system.
14

Figure 9. Test house floor plan
15

3.3 Testing Approach

The objective of the test program was to compare the whole-building, multizone, indoor air 

quality performance of continuous exhaust ventilation, CFIS ventilation, and ERV. The homes 

were completely finished, with kitchen and bathroom cabinets, but were unfurnished and 

unoccupied. This allowed an evaluation focus on the building elements themselves, avoiding 

conflation with occupant activities and items particular individuals bring into their homes. The 

testing approach taken was a combination of:

• Building enclosure and building mechanical systems characterization by measurement of 

building enclosure air leakage, central air distribution system airflows, and ventilation 

system airflows. 

• Field tracer gas work using per-fluorocarbon tracer gases (PFTs) to determine zone air 

change rates and interzonal airflows with different ventilation systems operating.

• Multizone sampling of volatile organic compounds (VOCs), formaldehyde (HCHO), and 

airborne particulates to determine indoor air quality impacts as a function of ventilation 

system operation.

• A preliminary CONTAM airflow network simulation model constructed from the

detailed building enclosure and building mechanical systems characterization testing (see 

Appendix B).

Table 3 provides a listing of the five tests conducted in each house, showing the designated test 

number, test name, and brief description. The test configurations were intended to represent 

normal limiting case conditions for most homes whereby space conditioning equipment may not 

operate for long periods (overnight to days long) and bedroom doors are closed at night.

The testing was originally planned for end of May to early June in order to avoid unreasonable 

indoor conditions without space conditioning operating, but that schedule could not be met, so 

the testing was delayed until early October. Figure 10 through Figure 12 show the indoor and 

outdoor conditions during each test period. Temperature and relative humidity (RH) in each zone 

and outside were measured with new HOBO U12-011 data loggers recording on a 5-minute 

interval. Wind direction and average and maximum values of wind speed were recorded on 5-

minute intervals by the data collection system that existed at the houses. The pole-mounted 

anemometer and wind vane were mounted on the roof of House 2.
16

Table 3. Test Number, Name, and Description of the Five Tests Conducted in Each House

Test 

Number Test Name Test Description

1 Baseline No ventilation, bedroom doors closed, no central fan operation

2 Exhaust

Exhaust ventilation from master bathroom, bathroom door 

open to bedroom, bedroom doors closed, no central fan 

operation

3 Exhaust with 

mixing

Exhaust ventilation from master bathroom, bathroom door 

open to bedroom, bedroom doors closed, 20% central fan 

operation (48 off/12 on)

4 CFIS CFIS ventilation, bedrooms closed, 33% central fan duty cycle 

(20 off/10 on)

5 ERV Balanced (ERV) ventilation, bedrooms closed, no central fan 

operation, 50% runtime (30 on/30 off)

Figure 10. House 1 temperature and RH in indoor zones and outdoors during each test period

40

50

60

70

80

90

100

110

Temperature [°F]

Outdoor

Main

Master

Middle

Front

Garage

Attic

20

30

40

50

60

70

80

90

100

Relative Humidity

Outdoor

Main

Master

Middle

Front

Garage

Attic
17

Figure 11. House 2 temperature and RH in indoor zones and outdoors during each test period

Figure 12. Wind speed during each of the test periods; green and red markers indicate start and 

stop of the 12-hour sampling periods

40

50

60

70

80

90

Temperature [°F]

Outdoor

Main

Master

Middle

Front

Garage

Attic

30

40

50

60

70

80

90

100

Relative Humidity

Outdoor

Main

Master

Middle

Front

Garage

Attic

0

2

4

6

8

10

12

Wind Speed (mph)
18

The first 12-hour period of each test was to achieve steady-state for the purposes of PFT, 

particulate, VOC, and HCHO sampling in the second 12-hour period of each test. The test 

sequence was scheduled such that the 12-hour period for sampling would be overnight. The PFT 

source emission rates are coarsely temperature dependent, which was accounted for in the 

analysis, but since we were not conditioning the buildings during the testing, we did not want to 

risk solar heating effects having an impact on the sources. We also wanted to limit wind as a

potentially confounding factor by taking advantage of generally lower wind conditions at night.

The overnight ventilation condition is a normal and important condition in homes and there was 

no need to complicate the testing and data analysis with external factors of daytime solar heating 

and wind. Figure 12 shows the start (green triangle marker) and stop (red triangle marker) times 

of the 12-hour sampling period of each test period, being evening to morning. The sixth test 

period shown in that Figure 12 is a retest of the House 2 baseline test.

A general note for all tests is that all closet doors were left open to allow that air volume to fully 

interact with the adjoining space, and all bedroom doors were configured to have the same 1⁄2 in.

undercut above the decoratively stained concrete floors throughout the houses.

The central system return air filters were new, 1-in. thick 3M Filtrete 700 filters, being given a 

“Better” ranking by the manufacturer (in a field of Good, Better, Best) and a Microparticle 

Performance Rating (MPR) of 700 (in a field of 300, 600, 700, 800, 1000, 1085, 1200, 1500, 

1900, and 2200). The MPR measures a filter’s ability to capture particles between 0.3 and 1.0 

micron. The manufacturer states that the Filtrete 700 used in this testing is intended for attracting 

and capturing some microscopic allergens like smoke and smog particles and large allergens like 

dust, mold spores, and pet dander from the air passing through the filter. The ASHRAE 

Minimum Efficiency Reporting Value (MERV) reports a filter’s ability to capture particles 

between 3 and 10 microns. Manufacturer literature has related the Filtrete 600 roughly to a 

MERV 8, the 1000 to a MERV 11, and the 1250 to a MERV 12 (IAQ Source 2013).

3.3.1 Baseline Test

The baseline test was conducted to benchmark all measured parameters with no ventilation 

system or space conditioning system operating.

3.3.2 Exhaust Test

The exhaust test was conducted using the master bathroom fan because BSC experience has been 

that that fan is most often the larger and better of the bathroom and toilet room fans in new 

houses. For testing, the continuous exhaust ventilation flow was adjusted to 45 cfm to meet the 

ASHRAE Standard 62.2-2010 continuous fan flow rate for the 1,475 ft2

, three-bedroom houses.

3.3.3 Exhaust With Mixing Test

The exhaust with mixing test was the same as the exhaust test except with a central system fan 

cycle of 48 minutes off and 12 minutes on. It was conducted to see the effects of trying to 

achieve better ventilation air distribution effectiveness via whole-house mixing of ventilation air 

drawn in by the exhaust fan through unknown locations in the building enclosure. The intent of 

the central system mixing was to achieve a 0.7 recirculation turnover factor which BSC has 

worked with the ASHRAE 62.2 Standard committee to implement. Additional exhaust 

ventilation testing was contemplated, using the lavatory bathroom off of the main area, but was 

eliminated due to budget constraints.
19

3.3.4 Central Fan Integrated Supply Test

The CFIS ventilation system test was conducted to evaluate the performance effects of drawing 

outside air from a planned outdoor air location, and filtering and fully distributing that air to each 

conditioned space zone. The outside air ventilation supply airflow was set at 135 cfm by means 

of a calibrated flow station (Iris damper), and the central system fan was controlled to operate on 

a 33% duty cycle, 20 minutes off/10 minutes on.

3.3.5 Energy Recovery Ventilator Test

The ERV test was conducted with a system independently ducted from the central air distribution 

system. The ERV ductwork in these houses was configured to exhaust from two locations in the 

main area and supply to all bedrooms. The ERV total supply airflow was measured to be 96 cfm 

so the ERV timer control was set for 50% runtime. The ERV included a washable course filter at 

the inlet of the heat and moisture energy recovery core within the unit. That filter was cleaned 

before testing began.

3.4 Building Enclosure, Central Air Distribution System, and Ventilation 

Systems Characterization

For each of the two test houses, the building enclosure, central air duct system, and the 

ventilation systems were characterized by the following procedures to facilitate PFT data 

interpretation and CONTAM modeling:

• Multipoint fan pressurization testing to establish the overall building enclosure air 

leakage rate.

• Multipoint, guarded and unguarded air leakage testing by fan pressurization of individual 

zones to determine the air leakage of the zone to exterior and zone-to-zone.

• Total duct leakage and duct leakage to outside testing.

• Central space conditioning system airflows.

• Local exhaust and whole-building ventilation system flow rates.

3.5 Per-Fluorocarbon Tracer Gas Testing

Each of the two houses was tested with six different tracer gas sources, one for each of the six

designated zones. The type and number of tracer gas sources used in each house and test are 

shown in Table 4. The PFT testing part of the project was set up and executed in consultation 

with Brookhaven National Laboratory (BNL) staff6 and in accordance with the prepared 

instructions provided by BNL (Dietz 2006) for the Air Infiltration Measurement System (AIMS).

Detailed explanation and statistical support for the PFT methods and AIMS analysis is provided 

in Leaderer et al. 1995 and Dodson et al. 2007.

 6 Terry Sullivan, PhD, Deputy Division Head, Environmental Research and Technology Division, Brookhaven 

National Laboratory, 75 Rutherford Drive, Building 815, Upton, NY 11973
20

Table 4. Type and Number of Tracer Gas Sources Used in Each House and Test

Zone Name Floor 

Area (ft2)

Height

(ft)

Volume

(ft3) PFT Color RSS Qty Resulting RSS Comment

House 1, Test 1 (10/3)

H1 Attic, Vented 1,463 9.2 13,507 PDCB Brown 1 1 1.00

H2 Attic, Unvented 1,463 9.2 13,507 PDCB Brown 1 1 1.00

Main 738 9.8 7,220 PMCH Red 0.93 1 0.93

Garage 419 9 3,771 PMCP Gold 0.62 1 0.62

Master Bedroom 337 8.2 2,766 ocPDCH Blue 0.16 5 0.80

Front Bedroom 165 9 1,485 1-2PTCH Silver 0.12 6 0.72

Middle Bedroom 159 8 1,272 iPPCH Purple 0.25 3 0.75

1⁄2 Bath (Open to Main) 64 8 512

House 2, Test 1 (10/3)

H1 Attic, Vented 1,463 9.2 13,507 PDCB Brown 1 1 1.00

H2 Attic, Unvented 1,463 9.2 13,507 PDCB Brown 1 1 1.00

Main 738 9.8 7,220 PMCH Red 0.93 1 0.93

Garage 419 9 3,771 PMCP Gold 0.62 1 0.62

Master Bedroom 337 8.2 2,766 1-2PTCH Silver 0.12 6 0.72

Master and front 

reversed relative 

to H1 for Test 1

Front Bedroom 165 9 1,485 ocPDCH Blue 0.16 5 0.80

Middle Bedroom 159 8 1,272 iPPCH Purple 0.25 3 0.75

1⁄2 Bath (Open to Main) 64 8 512

House 1 and House 2 Tests 2–5, And House 2 Test 6 (Beginning 10/4) (Re-Assigned To Optimize by Volume and Resulting Relative 

Source Strength)

H1 Attic, Vented 1,463 9.2 13,507 PDCB Brown 1 1 1.00

H2 Attic, Unvented 1,463 9.2 13,507 PDCB Brown 1 1 1.00

Main 738 9.8 7220 PMCH Red 0.93 1 0.93

Garage 419 9 3,771 ocPDCH Blue 0.16 5 0.80

Master Bedroom 337 8.2 2,766 iPPCH Purple 0.25 3 0.75

Front Bedroom 165 9 1,485 1-2PTCH Silver 0.12 6 0.72

Middle Bedroom 159 8 1,272 PMCP Gold 0.62 1 0.62

1⁄2 Bath (Open to Main) 64 8 512
21

The PFT sources supplied by BNL were contained in a metal tube (see Figure 14) and were

always emitting gas at a predictable rate through a stopper at the top. The emission rate of the 

PFT sources is affected by temperature, so temperature and RH were monitored in each zone and 

used by BNL in the analysis. Zone temperature and RH measurement was by new HOBO U12-

011 data loggers recording on a 5-minute interval. Per BNL instructions, a box fan placed in the

attics was used to facilitate mixing within that zone (see Figure 5). That is especially important

in vented attics to minimize wind-driven effects that could bias normal gas diffusion distribution 

of PFT source, where prevailing winds can dominate by pushing air in one side of the attic and 

out the other.

Between each test the PFT sources were sealed in doubled, heavy-duty resealable bags (bag 

within another bag) and left in their respective zones while the house was flushed with outdoor 

air to a minimum of 10 complete air changes using a blower door and open windows and doors.

An exhaust fan in the unvented attic aided flushing of that space to the garage attic and to 

outside. 

To start each test, the PFT sources were opened in their respective zones for 12 hours with the 

appropriate ventilation system operating to approach steady-state conditions. The PFT samplers

(CATS [Capillary Adsorption Tube Sampler]) were not deployed (capped and not near any 

sources) during that initial 12-hour period. Then, the samplers were placed in each zone and 

uncapped for the next 12 hours to complete the test.

A total of 60 primary samples were taken (two houses, five tests, six zones per test), and a total 

of 60 backup samplers were taken to be analyzed if data from any primary samples were suspect

or for general quality assurance (QA) and quality control (QC) purposes. All six backup 

samplers were analyzed for one test (H2-Test 2) based on an observation question (we wanted to 

verify the result that the attic to main airflow was low in House 2 compared to House 1) and for a

general QA/QC check. The results showed only minor differences between the two sets of data

and the AIMS airflow analysis (refer to Figure 26). Figure 14 shows primary and backup CATS 

mounted on the sampling fixture.

Figure 13. House 2 main zone with PFT source tripod on left and sampling station tripod on right
22

Figure 14. PFT source (left) and primary and backup CATS (right)

3.6 Airborne Particulate Sampling

During the 12-hour quasi steady-state period of each PFT test period, air sampling for airborne 

particulates was conducted in the main (common area) and master bedroom zones (see Figure 16

and Figure 17). During some tests, additional particulate sampling was done outdoors, and in the 

garage and attic of each house. Particulates were monitored at six particle sizes (0.3, 0.5, 1.0, 2.0, 

5.0, and 10.0 micrometer) with a Fluke model 985 laser airborne particle counter. The meter has 

a counting efficiency of 50% @ 0.3 μm and 100 % for particles > 0.45 μm. The sample flow rate

was 0.1 cfm (2.83 L/min). The meter was programmed to complete 48 cycles of 15-minute 

samples over the second 12-hour period of each test, gathering a sample volume of 1.5 ft3 (42.45 

L) each cycle. Data were recorded electronically and imported into a worksheet for analysis.

Only the last 21 15-minute particle counting cycles (cycles 20–40), or the last 5.25 hours before 

researchers re-entered the houses were used for analysis. This was to analyze the data closest to 

steady-state and to isolate the particle load attributable to the operation of different ventilation 

systems from any occupant (researcher) interaction. Occupant interaction can be significant, 

especially in the larger particle sizes as shown at the beginning and end of the test in Figure 15.
23

Figure 15. Cumulative particle counts for six particle sizes during the baseline test in House 2, 

main zone; results show impact on large particle counts due to human disturbance 1.5 hours

before end of sampling period

Figure 16. Test fixture tripod holding (left to right in photos) HCHO sample pump, temperature and 

relative humidity data logger, PFT sample tubes (CATS), airborne particulate counter, and VOC 

sampling pump

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

1 5 9 13 17 21 25 29 33 37 41 45

Cumulative Particle Counts

nth 15 minute sampling cycle 

Particulate Levels, House 2, Main zone, Baseline

H2 Main 0.3 micron

H2 Main 0.5 micron

H2 Main 1.0 micron

H2 Main 2.0 micron

H2 Main 5.0 micron

H2 Main 10.0 micron
24

3.7 Volatile Organic Compound Sampling

Ninety minutes before the end of the 12-hour steady-state period of each PFT test period, volatile 

organic compound (VOC) sampling was conducted in the main (common area) and master 

bedroom zones (see Figure 17). During some tests, additional VOC sampling was done in the 

garage and attic of each house. An 18-L air sample was collected in each case. The solid sorbent 

samplers and the calibrated low-flow sample pumps (0.2 L/min) were provided by Air Quality 

Sciences division of Underwriters Laboratory (UL-AQS). Laboratory analysis of the samples 

was also conducted by UL-AQS, with a report identifying the “Top 20” VOCs (by 

concentration) identified in each sample for each test.7

Figure 17. VOC sampling pump and solid sorbent sample tube; 

airborne particulate counter on top of sampling fixture

 7 VOC samples collected on solid sorbents and analyzed by thermal desorption/mass spectrometry according to AQS 

Method CLI023 (based on EPA Compendium Method TO-17 and ASTM 6196). Individual compounds and TVOCs 

(total volatile organic compounds) are calibrated relative to toluene. Values below 2.0 μg/m3 are for information 

purposes only. Chemical was detected, but below the quantifiable level of 0.04 μg based on a standard of 18 L air 

collection volume. AQS’ quality assurance program monitors blank sorbent media to ensure that the residual 

background does not exceed AQS’ quality objective of ≤ 36 ng of total VOC. Quality Assurance Report available at 

www.aqs.com.
25

3.8 Formaldehyde Sampling

Sixty minutes before the end of the 12-hour steady-state period of each PFT test period, HCHO 

sampling was conducted in the main (common area) and master bedroom zones (see Figure 16).

During some tests, additional VOC sampling was done in the garage and attic of each house. A 

60 L air sample was collected in each case. The DNPH samplers and the calibrated sample 

pumps (1.0 L/min) were provided by UL-AQS. Laboratory analysis of the samples was also 

conducted by UL-AQS, with a report identifying the HCHO concentration identified in each 

sample for each test.8

 8 Analysis by DNPH/HPLC according to AQS Method CLI022 (based on ASTM Method D5197). Any values 

below 2.0 μg/m3 are for information purposes only; chemical was detected, but below the quantifiable level of 0.12 

μg based on a standard of 60 L air collection volume. Reported concentrations based on 60.0 L of volume sampled. 

Field blanks are not intended to have a measurable amount of air sampled. Quality Assurance Report available at 

www.aqs.com.
26

4 Discussion of Results

4.1 Building Air Leakage Characterization

4.1.1 Fan Pressurization Tests

In June and October 2012, air leakage characterization of the two test houses was conducted 

using automated and non-automated fan pressurization techniques. Multiple calibrated fans 

(blower doors and duct blasters) were used, and pressure measurement was recorded in each 

zone with respect to outside. Table 5 gives the physical characteristics of each house needed for 

normalizing the test results. Detailed building and zonal leakage test results, including those 

from numerous guarded tests designed to assist with future modeling efforts, are given in 

Appendix B.

Table 5. Physical Characteristics of the Test Houses

Zone Name

Floor

Area 

(ft2

)

Max 

Height 

(ft)

Volume 

(ft3)

Perimeter

(ft)

Exterior 

Wall 

Area

(ft2

)

House 1

Exterior

Surface 

Areab (ft2)

House 2

Exterior

Surface 

Area2 (ft2)

Main 750 10.0 7220 47 472 1972 1222

Master 337 9.0 2766 48 433 1107 770

Middle 159 8 1272 13 100 418 259

Bath 64 8 512 6 50 178 114

Front 165 9 1485 35 315 645 480

House 1 Total 1475 44 13255 149 1370 4320

Attic (House 2)a 1475 13507 2860

House 2 Total 1475 44 26762 149 1370 5705

% diff. H2/H1 102% 32% a Attic volume and roof surface from AutoCAD 3D model

b Exterior surface area includes the slab floor, walls and roof

Typically reported summary results of blower door testing for each house are given in Table 6.

House 2, with the unvented attic house with spray foam under the roof deck, had 789 cfm50 

leakage compared to 1,048 cfm50 leakage for House 1 with a vented attic. Referring to Table 5, 

the volume and exterior surface area of House 2 are 102% and 32% greater than that of the 

House 1, respectively, illustrating the importance of air sealing the unvented attic.

4.2 HVAC Characterization

Table 7 gives the results of duct leakage testing for both houses, and Table 8 gives the results of 

the cooling system room airflow testing for each house. The heat pump systems were not 

identical between the houses, nor were the heating and cooling loads, so the difference in total 

airflow and room airflow was expected. The ventilation systems were set up to meet the 

ASHRAE Standard 62.2-2010 fan flow rate as shown in Table 9. 
27

Table 6. Typically Reported Blower Door Test Results For Each Test House

Conditioned

Floor

Area (ft2

)

Conditioned 

Volume 

(ft3)

a

Surface 

Areab C n CFM50 ACH50

CFM50/ft2

Surface 

Area

EqLAc

(in.

2

)

ELAd

(in.

2

) SLAe

House 

1 1,475 13,255 4,320 66.2 0.706 1048 4.74 0.24 99 49.94 2.35

House 

2 1,475 26,762 5,705 67.1 0.63 789 1.77 0.14 84 45.56 2.14

a

For House 2, volume includes the unvented attic which is inside the thermal enclosure but not actively conditioned

b Exterior surface area includes the slab floor, walls, and ceiling (House 1) or roof (House 2) c Equivalent leakage area; EqLA = CFM10 * 0.2939

d Effective leakage area; ELA = CFM4 * 0.2835 e Specific leakage area; SLA = ELA / 144 / floor area * 10,000
28

Table 7. Duct Leakage Tests

Duct Leakage

House 1 

(CFM25)

% of Total

Airflow

House 2 

(CFM25)

% of Total

Airflow

Total to Outside* 182 16% 217 31%

56 5% 30 4%

* Leakage to outside for House 2 is realistically zero. It is a typical artifact of that test that shows a non-zero value, 

due to the unvented attic “buffer zone” not being completely nulled to the duct pressure. 

Table 8. Central Air Distribution System (Heat Pump) Cooling Supply Airflows

Central AC Supply

Room House 1 (CFM) House 2 (CFM)

Living Room

89 43

104 44

122 60

97 59

134 82

98 125

Mechanical Room 69 26

Master Bedroom 187 64

Master Bath 74 20

Master Closet 33 21

Middle Bedroom 63 67

Bath 2 42 21

Front Bedroom 25 75

Supply Total 1137 707

Table 9. Ventilation System Airflow and Runtime Setup

Exhaust (100% Runtime)

Room House 1 (CFM) House 2 (CFM)

Master Bathroom 45 45

CFIS (33% Runtime)

Flow Station 135 135

Outside Air Intake 109 100

ERV (50% Runtime)

Master Supply 36 47

Middle Supply 27 25

Front Supply 30 24

Supply Total 93 96

Outside Air Intake 116 96

Exhaust Foyer 58 48

Exhaust Kitchen 80 75

Exhaust Total 138 123
29

4.3 Per-Fluorocarbon Tracer Gas testing

PFT testing provided detailed information separately on individual zone outside air change rates

and interzonal airflows. The testing materials were provided by BNL, the testing was done by 

BSC, the AIMS analysis was done by BNL, and the analysis and presentation of the AIMS 

results was done by BSC.

4.3.1 Zone Air Change Rates

Figure 18 shows the individual zone air change rates for different ventilation systems in House 1.

The air change rates were averaged over the final 12 hours of each 24-hour test. Infiltration and 

mechanically induced air change were combined in the PFT outside air change rate 

measurements. Fortunately, temperature differentials and wind speed were reasonably stable and 

similar during the testing periods so as to allow good comparison of zonal air change rates

between the ventilation systems. The baseline test (no mechanical ventilation) showed low air 

change rates throughout all zones, with the lowest being the master and middle bedroom zones. 

Continuous exhaust ventilation from the master bathroom increased the air exchange by about 

0.1 ach over baseline in the main and master zones, but the increase was less in the middle and 

front zones where the total air exchange rate remained below 0.1 ach. Exhaust with mixing (12 

min/h via the central air distribution system) significantly improved the air change rate over 

exhaust-only in the middle and front zones. CFIS showed a significant improvement in air 

change rate over exhaust-only in all but the main zone. CFIS showed an improvement over 

exhaust with mixing only in the master zone. The balanced ERV showed huge air change rate 

increases in the bedrooms but was about the same as the other ventilation systems in the main 

zone. That was by design since the ERV supplied fresh air only to the bedrooms and exhausted 

air only from the main zone.
30

Figure 18. Air change rates in the living space zones for House 1, 

for the baseline test and four different ventilation systems

Figure 19 shows the measured air change rates in the garage and vented attic zones for House 1.

The garage air change rate for all tests, regardless of ventilation system, was similar to the 

baseline rates in the living space zones. The vented attic air change rate was about 0.65 ach for 

all tests except it was double that for the exhaust with mixing test. That can be explained by 

referring to Figure 12 and observing the wind speed during the sampling part (last 12 hours) of 

each test. The wind speed was 4–8 mph for the exhaust with mixing test whereas it was 0–2 mph 

for all the other tests.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Main Master Middle Front

Zone ACH (1/h)

Zone Location

House 1: Living Space Air Change Rates

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV

0.00

0.05

0.10

0.15

Main Master Middle Front

Stardard Deviation 

(1/h)

Zone Location

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV
31

Figure 19. Measured air change rates in the garage and attic zones for House 1, 

for different ventilation systems

Comparing Figure 18 and Figure 20, it is evident that the living zone air change rates exhibit the 

same trends for both houses, confirming the reliability of the test methods. Comparing Figure 19

and Figure 21, the same is true for the garage zones.

As expected, the attic zones respond differently between the houses. In the unvented attic of 

House 2, the air change rates were very low, between about 0.02 and 0.04, for the baseline, 

CFIS, and ERV tests. The air change rate increased fivefold, to between 0.16 and 0.18 ach, for 

both the exhaust and the exhaust with mixing ventilation systems. That points to the exhaust 

ventilation system drawing ventilation air from the attic.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Garage Vented Attic

Zone ACH (1/h)

Zone Location

House 1: Garage and Attic Air Change Rates

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV

0.00

0.05

0.10

0.15

0.20

Garage Vented Attic

Standard Deviation 

(1/h)

Zone Location

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV
32

Figure 20. Air change rates in the living space zones for House 2 (unvented attic), for the baseline

test and four different ventilation systems, showing the same trends as House 1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Main Master Middle Front

Zone ACH (1/h)

Zone Location

House 2: Living Space Air Change Rates

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV

0.00

0.05

0.10

Main Master Middle Front

Standard Deviation 

(1/h)

Zone Location

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV
33

Figure 21. Measured air change rates in the garage and unvented attic zones for House 2, 

for the baseline test and four different ventilation systems

4.3.2 Interzonal Airflows

As understood from the standard deviation results provided with the BNL AIMS analysis,9 the 

measured interzonal airflows have a higher degree of uncertainty than the zonal air change rates.

However, they serve a valuable purpose in at least confirming airflow in expected directions and 

indicating the reliability of the PFT measurements. As shown in Figure 22 and Figure 23, and as 

could be expected, the airflow from the garage to the main zone was the highest for the exhaust 

ventilation systems. Airflow from the garage to the main zone was the lowest for the CFIS 

ventilation system and between exhaust and CFIS for the ERV system. As a theoretically 

balanced system, the ERV system might be expected to behave just like the baseline, but the fact 

that the ERV system was designed to supply to the bedrooms and exhaust from the main zone set 

up a mechanically induced airflow imbalance within the multizone structure (main being 

negative and bedrooms being positive) that shows up in this measurement. Airflow from the

garage to the bedroom zones was essentially negligible for all tests, but even so, airflow to the 

master zone was slightly higher for the exhaust systems, as makes sense since the exhaust fan 

was located there.

 9 The AIMS error analysis uses a 5% error in the estimate of the volume of the room, a 7% error in the source 

emission rate, and a 10% error in the CATS PFT concentration when there is only a single CATS in the zone. A full 

description of the error analysis is in Leadererr et al. 1995.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

Garage Unv Attic

Zone ACH (1/h)

Zone Location

House 2: Garage and Attic Air Change Rates

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV

0.00

0.01

0.02

0.03

Garage Unv Attic

Standard Deviation 

(1/h)

Zone Location

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV
34

Figure 22. Airflow from garage to living area zones in House 1, for the baseline test and four 

different ventilation systems

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Garage to 

Main

Garage to 

Master

Garage to 

Middle

Garage to 

Front

Interzonal Airflow (ft3/min)

Garage to Living Zones Airflow for House 1

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Garage to 

Main

Garage to 

Master

Garage to 

Middle

Garage to 

Front

Standard Deviation 

(ft3/min)

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV
35

Figure 23. Airflow from garage to living area zones in House 2, for the baseline test and four 

different ventilation systems, showing the same trends as House 1

Airflow from the attic (vented) to the living space zones for House 1 is shown in Figure 24. The 

Exhaust with mixing system consistently shows the highest airflow from the attic, followed by 

exhaust, CFIS, ERV, and baseline. By comparing the results for House 1 (Figure 24) with House 

2 (Figure 25), it becomes clear that:

• The exhaust system was moving 20% of its ventilation air (10 cfm) from the vented attic 

in House 1 to the main zone. About 7 cfm or another 14% of the exhaust ventilation air in 

House 1 was moving from the attic to the bedroom zones. A total of 34% (17 cfm out of 

50) of the ventilation air for the exhaust system in House 1 was coming from the vented 

attic. In comparison, for the unvented attic of House 2, the exhaust system moved only 

2% of its ventilation air from the attic to the main zone. This indicates that the exhaust 

makeup air path to outside was more resistive through the unvented attic spray-foamed 

roof than through the vented attic ceiling with recessed light penetrations. Because of 

this, the exhaust ventilation system performed somewhat better in the unvented attic 

house.

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Garage to 

Main

Garage to 

Master

Garage to 

Middle

Garage to 

Front

Interzonal Airflow (ft3/min)

Garage to Living Zones Airflow for House 2

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV

0.0

0.2

0.4

0.6

0.8

Garage to 

Main

Garage to 

Master

Garage to 

Middle

Garage to 

Front

Standard Deviation 

(ft3/min)

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV
36

• In both houses, some central air distribution system return side leakage is causing the 

CFIS and exhaust with mixing ventilation systems to move about 10 cfm of attic air to 

the main zone. However, there is a big difference in ventilation effectiveness between the 

10 cfm in a) and the 10 cfm in b). In a), it is 10 cfm out of 50 cfm of what was expected

to be good ventilation air, whereas in b) it is 10 cfm out of 1000 cfm of recirculated and 

conditioned/filtered air. For the CFIS system, the full amount of expected outside air was 

still being delivered from a known outdoor intake location, whereas for the exhaust 

system of House 1, 34% of the expected outside air was from the vented attic.

Figure 24. Airflow from attic to living area zones in House 1, 

for the baseline test and four different ventilation systems

0

2

4

6

8

10

12

14

Attic to 

Main

Attic to 

Master

Attic to 

Middle

Attic to 

Front

Interzonal Airflow (ft3/min)

Attic to Living Zones Airflow for House 1

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV

0

1

2

3

4

5

6

7

Attic to 

Main

Attic to 

Master

Attic to 

Middle

Attic to 

Front

Standard Deviation 

(ft3/min)

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV
37

Figure 25. Airflow from attic to living area zones in House 2, 

for the baseline test and four different ventilation systems

Figure 26 shows interzonal airflows for a single case—House 2, Test 2 (exhaust)—where the 

backup CATS were analyzed as a quality assurance/quality control check on the PFT test and 

analysis method. There was a strong showing of consistency in results between the two sets of 

simultaneous samples.

0

2

4

6

8

10

12

14

Attic to 

Main

Attic to 

Master

Attic to 

Middle

Attic to 

Front

Interzonal Airflow (ft3/min)

Attic to Living Zones Airflow for House 2

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV

0

1

2

3

4

5

Attic to 

Main

Attic to 

Master

Attic to 

Middle

Attic to 

Front

Standard Deviation 

(ft3/min)

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV
38

Figure 26. Backup CATS analyzed for QA/QC check; House 2, Test 2 (exhaust)

Figure 27 through Figure 30 show interzonal airflows for the living space zones in both 

directions. In terms of internal air distribution, the baseline system showed little interzonal

airflow in all cases, which was expected and confirmed that at least the trends indicated by the 

interzonal airflow results were reliable. All systems showed little interzonal airflow between 

bedrooms. As expected with the largest central air distribution system return air inlet in the main 

zone, the most interzonal airflow was between the main zone and bedroom zones for the CFIS 

and exhaust with mixing cases. The exhaust cases showed significant airflow (about 15 cfm) 

from main to master and no airflow in the reverse direction, as expected with the exhaust fan 

located in the master zone. Otherwise, the exhaust systems showed little interzonal airflow and 

distribution of ventilation air. The ERV system showed little airflow from main to bedrooms and 

between bedrooms, but relatively high airflow (10–20 cfm) from bedrooms to the main zone, as 

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

Master to Main

Middle to Main

Front to Main

Middle to Master

Front to Master

Front to Middle

Garage to Main

Garage to Master

Garage to Middle

Garage to Front

Attic to Main

Attic to Master

Attic to Middle

Attic to Front

Interzonal Airflow (ft3/min)

Backup CATS analyzed for QA/QC for House 2, Test 2 

H2-exhaust H2-exhaust backups

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Master to Main

Middle to Main

Front to Main

Middle to Master

Front to Master

Front to Middle

Garage to Main

Garage to Master

Garage to Middle

Garage to Front

Attic to Main

Attic to Master

Attic to Middle

Attic to Front

Standard Deviation (ft3/min)

H2-exhaust H2-exhaust backups
39

expected since the ERV system supplied fresh air to the bedrooms and exhausted stale air from 

the main zone.

Figure 27. House 1 interzonal airflows for living space zones

-5

0

5

10

15

20

25

30

35

40

Main 

to 

Master

Main 

to 

Middle

Main 

to 

Front

Master 

to 

Middle

Master 

to 

Front

Middle 

to 

Front

Interzonal Airflow (ft3/min)

Interzonal Airflows for House 1

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV

0

5

10

15

20

25

Main 

to 

Master

Main 

to 

Middle

Main 

to 

Front

Master 

to 

Middle

Master 

to 

Front

Middle 

to 

Front

Standard Deviation 

(ft3/min)

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV
40

Figure 28. House 1 reverse direction interzonal airflows for living space zones

-10

0

10

20

30

40

50

60

Master 

to 

Main

Middle 

to 

Main

Front 

to 

Main

Middle 

to 

Master

Front 

to 

Master

Front 

to 

Middle

Interzonal Airflow (ft3/min)

Interzonal Airflows for House 1 (rev. direction)

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV

0

5

10

15

20

25

30

Master 

to 

Main

Middle 

to 

Main

Front 

to 

Main

Middle 

to 

Master

Front 

to 

Master

Front 

to 

Middle

Standard Deviaion 

(ft3/min)

H1-baseline

H1-exhaust

H1-exhaust w/mixing

H1-CFIS

H1-ERV
41

Figure 29. House 2 interzonal airflows for living space zones

-2

0

2

4

6

8

10

12

14

16

18

20

Main to 

Master

Main to 

Middle

Main to 

Front

Master 

to 

Middle

Master 

to 

Front

Middle 

to 

Front

Interzonal Airflow (ft3/min)

Interzonal Airflows for House 2

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV

0

1

2

3

4

5

6

7

Main 

to 

Master

Main 

to 

Middle

Main 

to 

Front

Master 

to 

Middle

Master 

to 

Front

Middle 

to 

Front

Standard Deviation 

(ft3/min)

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV
42

Figure 30. House 2 reverse direction interzonal airflows for living space zones

4.4 Airborne Particulate Sampling

As mentioned above, only the last 21 15-minute particle counting cycles before researchers reentered the houses, or the last 51⁄4 hours of the 12-hour sampling period, were used for analysis 

presentation. This was to isolate the particle load due to the operation of different ventilation 

system from any occupant (researcher) interaction. Occupant interaction was easy to see in the 

full set of data, having a large impact on large particles but little impact on the smallest particles.

As mentioned above, particulates were monitored at six particle sizes (0.3, 0.5, 1.0, 2.0, 5.0, 10.0 

micrometer) with a Fluke model 985 laser airborne particle counter. The meter has a counting 

efficiency of 50 % @ 0.3 μm and 100 % for particles > 0.45 μm. The sample flow rate was 0.1 

cfm (2.83 L/min). The meter was programmed to complete 48 cycles of 15-minute samples over 

the second 12-hour period of each test, gathering a sample volume of 1.5 ft3 (42.45 L) each 

cycle. Data were recorded electronically and imported into a worksheet for analysis. Only the 

last 21 15-minute particle counting cycles, or the last 51⁄4 hours before anyone re-entered the 

houses were used for analysis. This was to analyze the data closest to steady-state and to isolate 

the particle load due to the operation of different ventilation system from any occupant 

interaction. Occupant interaction was easy to observe in the full set of data, having a large impact 

on the largest particles but little impact on the smallest particles.

-5

0

5

10

15

20

25

30

35

40

Master 

to 

Main

Middle 

to 

Main

Front 

to 

Main

Middle 

to 

Master

Front 

to 

Master

Front 

to 

Middle

Interzonal Airflow (ft3/min)

Interzonal Airflows for House 2 (rev. direction)

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV

0

1

2

3

4

5

6

7

8

Master 

to 

Main

Middle 

to 

Main

Front 

to 

Main

Middle 

to 

Master

Front 

to 

Master

Front 

to 

Middle

Standard Deviation 

(ft3/min)

H2-baseline

H2-exhaust

H2-exhaust w/mixing

H2-CFIS

H2-ERV
43

While this report is not intended to address the detailed human health concerns related to particle 

contaminants, a little background is useful here. Small particles are considered hazardous to 

human health. Particle sizes of 10 micrometers (micron or μm) or less are generally not filtered 

by the nose and throat and reach the lungs. Particle sizes of 2.5 micrometers and less can enter 

into the gas exchange region of the lung. Particles sizes of 0.1 micrometer and less can pass 

through the lung to organs, including the heart and brain.

In rough perspective, bacteria, mold spores, and dust mite allergens can all be 10 microns or less.

Cat allergens, tobacco smoke, soot, and smog can all be 1 micron or less. Viruses, tobacco 

smoke, soot, and smog can all be 0.1 micron or less.

Figure 31 shows plots of the cumulative10 particle counts for House 1, for all six particle sizes 

and ventilation systems, for the main and master zones side-by-side. Figure 32 shows the same 

thing for House 2. There was not an important difference in particulate levels between the main 

and master zones, but there was an important and consistent difference found between the 

ventilation systems. The highest levels were found for the exhaust system, followed by the 

baseline or ERV, followed by the exhaust with mixing and CFIS. CFIS always showed the 

lowest particle counts regardless of particle size. As would be expected, this indicated that the 

Filtrete 700 filters (700 MPR and roughly MERV 9) in the central air distribution system return 

air grilles were removing a significant amount of particle contaminant 0.3 micron and larger.

 10 The cumulative particle count reported throughout this study gives the sum of particles counted that were greater 

than or equal to threshold particle size given. For example, a cumulative particle count of 1,000 for the 2.0 micron 

size means that there were 1,000 particles of size ≥ 2.0 micron. Differential particle size can be calculated by 

subtracting the cumulative particle count of the next larger size from the cumulative particle count of the smaller 

size. For example, if the cumulative particle count was 1,000 and 10,000 for particle sizes 2.0 micron and 1.0 

micron, respectively, then the differential particle count would be 9,000 particles between 1.0 and 2.0 micron size.
44

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

0.3 μm Particle Size, House 1, Main

H1 Main exhaust

H1 Main ERV

H1 Main baseline

H1 Main exh w/mixing

H1 Main CFIS

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle

0.3 μm Particle Size, House 1, Master

H1 Master exhaust

H1 Master ERV

H1 Master baseline

H1 Master exh 

w/mixing

H1 Master CFIS

0

50,000

100,000

150,000

200,000

250,000

300,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

0.5 μm Particle Size, House 1, Main

H1 Main exhaust

H1 Main ERV

H1 Main baseline

H1 Main exh w/mixing

H1 Main CFIS

0

50,000

100,000

150,000

200,000

250,000

300,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle

0.5 μm Particle Size, House 1, Master

H1 Master exhaust

H1 Master ERV

H1 Master baseline

H1 Master exh 

w/mixing

H1 Master CFIS

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

1.0 μm Particle Size, House 1, Main

H1 Main exhaust

H1 Main ERV

H1 Main baseline

H1 Main exh w/mixing

H1 Main CFIS

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle

1.0 μm Particle Size, House 1, Master

H1 Master exhaust

H1 Master ERV

H1 Master baseline

H1 Master exh 

w/mixing

H1 Master CFIS

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

2.0 μm Particle Size, House 1, Main

H1 Main exhaust

H1 Main ERV

H1 Main baseline

H1 Main exh w/mixing

H1 Main CFIS

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle

2.0 μm Particle Size, House 1, Master

H1 Master exhaust

H1 Master ERV

H1 Master baseline

H1 Master exh 

w/mixing

H1 Master CFIS
45

Figure 31. Cumulative particle counts for six particle sizes (0.3–10 micrometer) for the House1 

main and master zones

0

10

20

30

40

50

60

70

80

90

100

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

5.0 μm Particle Size, House 1, Main

H1 Main exhaust

H1 Main ERV

H1 Main baseline

H1 Main exh w/mixing

H1 Main CFIS

0

10

20

30

40

50

60

70

80

90

100

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle

5.0 μm Particle Size, House 1, Master

H1 Master exhaust

H1 Master ERV

H1 Master baseline

H1 Master exh 

w/mixing

H1 Master CFIS

0

2

4

6

8

10

12

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

10.0 μm Particle Size, House 1, Main

H1 Main exhaust

H1 Main ERV

H1 Main baseline

H1 Main exh w/mixing

H1 Main CFIS

0

2

4

6

8

10

12

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle

10.0 μm Particle Size, House 1, Master

H1 Master exhaust

H1 Master ERV

H1 Master baseline

H1 Master exh 

w/mixing

H1 Master CFIS
46

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

9,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

0.3 μm Particle Size, House 2, Main

H2 Main exhaust

H2 Main exhaust(2)

H2 Main ERV

H2 Main baseline

H2 Main exh w/mixing

H2 Main CFIS

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

9,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

0.3 μm Particle Size, House 2, Master

H2 Master exhaust

H2 Master exhaust(2)

H2 Master ERV

H2 Master baseline

H2 Master exh 

w/mixing

H2 Master CFIS

0

100,000

200,000

300,000

400,000

500,000

600,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

0.5 μm Particle Size, House 2, Main

H2 Main exhaust

H2 Main exhaust(2)

H2 Main ERV

H2 Main baseline

H2 Main exh w/mixing

H2 Main CFIS

0

100,000

200,000

300,000

400,000

500,000

600,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

0.5 μm Particle Size, House 2, Master

H2 Master exhaust

H2 Master exhaust(2)

H2 Master ERV

H2 Master baseline

H2 Master exh 

w/mixing

H2 Master CFIS

0

5,000

10,000

15,000

20,000

25,000

30,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

1.0 μm Particle Size, House 2, Main

H2 Main exhaust

H2 Main exhaust(2)

H2 Main ERV

H2 Main baseline

H2 Main exh w/mixing

H2 Main CFIS

0

5,000

10,000

15,000

20,000

25,000

30,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

1.0 μm Particle Size, House 2, Master

H2 Master exhaust

H2 Master exhaust(2)

H2 Master ERV

H2 Master baseline

H2 Master exh 

w/mixing

H2 Master CFIS

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

2.0 μm Particle Size, House 2, Main

H2 Main exhaust

H2 Main exhaust(2)

H2 Main ERV

H2 Main baseline

H2 Main exh w/mixing

H2 Main CFIS

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

2.0 μm Particle Size, House 2, Master

H2 Master exhaust

H2 Master exhaust(2)

H2 Master ERV

H2 Master baseline

H2 Master exh 

w/mixing

H2 Master CFIS
47

Figure 32. Cumulative particle counts for six particle sizes (0.3–10 micrometer) for the House 2 

main and master zones

Table 10 provides a more detailed analysis of the particle count data in the range of 0.3–2.0 

micron. Differential particle counts over the range of 0.3–2.0 micron were calculated from the 

cumulative particle counts for the main and master zones. The percent difference in differential 

particle counts was shown compared to the exhaust ventilation system. The average percent 

difference showed a 69%–85% reduction in small particles over the exhaust-only system in 

House 1, and a 52%–73% reduction in House 2. The CFIS ventilation system showed the 

greatest reduction in small particles for both houses, attributable to recirculation air filtration by 

operation of the central air distribution system. 

0

20

40

60

80

100

120

140

160

180

200

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

5.0 μm Particle Size, House 2, Main

H2 Main exhaust

H2 Main exhaust(2)

H2 Main ERV

H2 Main baseline

H2 Main exh w/mixing

H2 Main CFIS

0

20

40

60

80

100

120

140

160

180

200

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

5.0 μm Particle Size, House 2, Master

H2 Master exhaust

H2 Master exhaust(2)

H2 Master ERV

H2 Master baseline

H2 Master exh 

w/mixing

H2 Master CFIS

0

2

4

6

8

10

12

14

16

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

10.0 μm Particle Size, House 2, Main

H2 Main exhaust

H2 Main exhaust(2)

H2 Main ERV

H2 Main baseline

H2 Main exh w/mixing

H2 Main CFIS

0

2

4

6

8

10

12

14

16

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

10.0 μm Particle Size, House 2, Master

H2 Master exhaust

H2 Master exhaust(2)

H2 Master ERV

H2 Master baseline

H2 Master exh 

w/mixing

H2 Master CFIS
48

Table 10. Calculation of Differential Particle Counts Over the Range of 0.3–2.0 Micron; 

the Percent Differences in Differential Counts Are Shown Compared to the Exhaust Ventilation System

Test

#

Main Zone Master Zone

Ventilation

System

Cumulative

Counts* at 

0.3 μm

Cumulative

Counts* at 

2.0 μm

Differential

Counts

0.3–2.0 μm

% Diff.

From

Exhaust

Cumulative

Counts* at 

0.3 μm

Cumulative

Counts* at 

2.0 μm

Differential

Counts

0.3–2.0 μm

% Diff.

From

Exhaust

Average

% Diff.

House 1

1 Baseline 2,764,437 2,992 2,761,446 –47% 2,453,086 1,871 2,451,215 –47% –47%

2 Exhaust 5,223,259 3,917 5,219,341 – 4,654,361 3,087 4,651,275 – –

3 Exhaust 

w/mixing 1,407,415 1,557 1,405,858 –73% 1,299,948 1,066 1,298,882 –72% –73%

4 CFIS 730,706 1,209 729,497 –86% 774,120 942 773,178 –83% –85%

5 ERV 1,522,578 2,120 1,520,458 –71% 1,572,288 2,652 1,569,636 –66% –69%

House 2

1(6) Baseline 3,171,002 2,611 3,168,391 –39% 3,745,584 2,061 3,743,523 –20% –29%

2 Exhaust 8,009,169 7,086 8,002,084 – 8,279,091 7,795 8,271,296 – –

3 Exhaust 

w/mixing 2,582,948 4,536 2,578,411 –51% 2,887,309 4,900 2,882,409 –38% –44%

4 CFIS 1,221,080 2,258 1,218,822 –77% 1,445,509 2,130 1,443,379 –69% –73%

5 ERV 2,277,061 2,882 2,274,178 –56% 2,396,952 2,935 2,394,018 –49% –52%

* Cumulative counts per 15-minute sample, averaged over 21 samples starting at hour 16.75 and ending at hour 22 of each 24 hour test period
49

Particulate measurements in the attics and garages are shown in Figure 33. For House 1, the 

measurements were taken in the attic during the ERV test, and in the garage during the CFIS test.

For House 2, the measurements were taken in the attic and the garage during two different 

baseline tests. The levels of particulate were reasonably close between the attic and garage of 

each individual house. House 1 had somewhat lower particulate levels than House 2 in the 

smallest particle sizes, they were nearly the same for the 1.0 micron size, then House 2 had lower 

levels in the 2.0 micron size and larger. The attic and garage in both houses had somewhat lower 

particulate levels than outside (Figure 34), particularly in the larger particle sizes.

The two outside tests were made outside of House 2 during two baseline tests. The second 

baseline test was made for House 2 because of inadvertent exhaust fan usage during the first 

baseline test. Indoor and outdoor temperature and relative humidity were similar during both 

tests. Wind speed was a little higher during the second test but the outside sample location was 

somewhat sheltered from wind. The particle count results of the two outside tests show 

remarkable consistency in Figure 34 and Table 11, indicating good measurement repeatability.

We did not have enough meters to measure outdoor particulate for each test, however, the 

measurements from these two tests, bracketing the entire testing period, were consistent with 

each other and essentially unchanging for 12 hours at a time. There were no obvious sources 

nearby in this suburban location, or weather disturbances that would give particular reason to 

think that outdoor particulate conditions would have changed much between test day 1 and test 

day 6 any more than they did on test day 1 and test day 6.

Table 11. Cumulative Particle Counts Measured Outdoors and in the House 1 and House 2 Attics

Particle

Size (μm)

Cumulative Particle Counts

Outdoor

Day 1

Outdoor

Day 6

Outdoor

Average H1 Attic

H1 Attic

% Diff 

From

Outdoor

Average

H2 Attic

H2 Attic

% Diff 

From

Outdoor

Average

H2 

Attic

% 

Diff 

From 

H1 

Attic

0.3 4,995,436 4,432,017 4,713,727 1,051,088 –78% 3,322,588 –30% 216%

0.5 316,595 363,054 339,824 55,715 –84% 179,863 –47% 223%

1.0 47,818 39,839 43,829 8,898 –80% 5,550 –87% –38%

2.0 24,710 13,569 19,140 2,871 –85% 797 –96% –72%

5.0 2,063 1,409 1,736 121 –93% 41 –98% –66%

10.0 294 291 292 15 –95% 8 –97% –49%

Cumulative particle counts, measured twice outdoors and in each attic, are shown in Table 11. 

The House 2 unvented attic air had an average of 220% more particles in the 0.3–0.5 micron 

range, but an average of 55% less particles in the 1.0–2.0 micron range. The air sampled in both 

attics had fewer particles than outdoors for all particle sizes. The air in the vented attic may 

continue to have fewer particles than outdoors because the attic is sheltered from wind, however, 

over time, the vented attic floor will accumulate particles much faster than the unvented attic 

floor. Where exhaust ventilation systems draw air from the attic, that air should pick up fewer

particles from the unvented attic floor than from the more dirty vented attic floor.
50

Table 12. Cumulative and Differential Particle Counts Measured Outdoors 

During Baseline Tests on the First and Last Test Days 

Outside

Test

#

Ventilation

System

Cumulative

Counts at 0.3 μm

Cumulative

Counts at 2.0 μm

Differential Counts

0.3–2.0 μm

1 Baseline 4,995,436 24,710 4,970,725

1(6) Baseline 4,432,017 13,569 4,418,448

Figure 35 shows the particle count measurements during the second Baseline test, comparing the 

coincident outside and inside results for the main and master zones, respectively. In both cases, 

the inside and outside particle counts are nearly the same for the 0.3 and 0.5 micron particle 

sizes. For 1.0 micron particles, the inside counts were about 5 times lower than outside. That 

trend increased progressively to about 100 times lower for inside counts compared to outside 

counts at the 10.0 micron size.
51

Figure 33. Cumulative particle counts for six particle sizes (0.3–10 micrometer) for the attic and 

garage zones for House 1 and House 2

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

Particle Size, H1, Attic (ERV) and Garage (CFIS)

H1 Attic 0.3 micron

H1 Garage 0.3 micron

H1 Attic 0.5 micron

H1 Garage 0.5 micron

H1 Attic 1.0 micron

H1 Garage 1.0 micron

H1 Attic 2.0 micron

H1 Garage 2.0 micron

H1 Attic 5.0 micron

H1 Garage 5.0 micron

H1 Attic 10.0 micron

H1 Garage 10.0 micron

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

Particle Size, H2, Attic and Garage (Baseline)

H2 Attic 0.3 micron

H2 Garage 0.3 micron

H2 Attic 0.5 micron

H2 Garage 0.5 micron

H2 Attic 1.0 micron

H2 Garage 1.0 micron

H2 Attic 2.0 micron

H2 Garage 2.0 micron

H2 Attic 5.0 micron

H2 Garage 5.0 micron

H2 Attic 10.0 micron

H2 Garage 10.0 micron
52

Figure 34. Cumulative particle counts for six particle sizes (0.3–10 micrometer) sampled outside 

on the first and last test days (test day 1 and test day 6)

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

Outside, Two Separate Tests (Day 1, Day 6)

Outside1 0.3 micron

Outside2 0.3 micron

Outside1 0.5 micron

Outside2 0.5 micron

Outside1 1.0 micron

Outside2 1.0 micron

Outside1 2.0 micron

Outside2 2.0 micron

Outside1 5 micron

Outside2 5.0 micron

Outside1 10.0 micron

Outside2 10.0 micron
53

Figure 35. Cumulative particle counts for six particle sizes (0.3–10.0 micron) for simultaneous 

measurements made outside and inside during the H2 baseline test

4.5 Formaldehyde Sampling

HCHO was sampled in the main and master zones in the last hour of each 24-hour test period.

Table 13 provides the numerical results and Figure 36 graphically illustrates the relative 

concentrations during the baseline test and the four ventilation system tests. Outside HCHO 

concentration was not measured at this location, but can generally be taken to be 2–3 ppb (2.5–

3.7 μg/m3) for this region of Texas (EPA 1991).

In House 1, all ventilation systems reduced the HCHO concentration over the indoor baseline

concentration which was roughly 20 times higher than what would be expected outdoors.

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

Coincident Outside and H2 Main baseline

H2 Main 0.3

Outside2 0.3 micron

H2 Main 0.5

Outside2 0.5 micron

H2 Main 1.0

Outside2 1.0 micron

H2 Main 2.0

Outside2 2.0 micron

H2 Main 5.0

Outside2 5.0 micron

H2 Main 10.0

Outside2 10.0 micron

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

20 22 24 26 28 30 32 34 36 38 40

Cumulative Particle Counts

nth 15 minute sampling cycle 

Coincident Outside and H2 Master baseline

H2 Master 0.3

Outside2 0.3 micron

H2 Master 0.5

Outside2 0.5 micron

H2 Master 1.0

Outside2 1.0 micron

H2 Master 2.0

Outside2 2.0 micron

H2 Master 5.0

Outside2 5.0 micron

H2 Master 10.0

Outside2 10.0 micron
54

Exhaust-only ventilation reduced the indoor HCHO concentration the least, followed by exhaust 

with mixing, CFIS, and ERV. Exhaust with mixing likely reduced the concentration over

exhaust-only because exhaust-only interacted more with the main and master zones than with the 

front and middle bedroom zones. Whole-house mixing averaged conditions such that 

concentrations in the main and master zones were lower.

In House 2, the exhaust systems either increased or did not appreciably change the HCHO 

concentration in the main and master zones. The CFIS and ERV systems showed a significant 

reduction in HCHO concentration over the baseline, and exhaust tests. In general for both 

houses, the CFIS and ERV systems showed a 60%–70% reduction in HCHO concentration over 

exhaust.

Table 13. HCHO Concentrations in House 1 and House 2, 

for the Baseline Test and Four Different Ventilation Systems

Description HCHO Concentration

ug/m3 ppb

H1 Baseline Main 68 56

H1 Baseline Master 71 58

H1 Exhaust Main 51 42

H1 Exhaust Master 53 44

H1 Exhaust W/Mixing Main 42 34

H1 Exhaust W/Mixing Master 40 33

H1 CFIS Main 19 15

H1 CFIS Master 17 14

H1 ERV Main 16 13

H1 ERV Master 11 9

H1 Exhaust W/Mixing Attic 9 8

H1 Exhaust W/Mixing Garage 25 21

H2 Baseline Main 40 33

H2 Baseline Master 23 19

H2 Exhaust Main 39 32

H2 Exhaust Master 37 30

H2 Exhaust W/Mixing Main 36 29

H2 Exhaust W/Mixing Master 32 26

H2 CFIS Main 22 18

H2 CFIS Master 20 16

H2 ERV Main 17 14

H2 ERV Master 11 9

H2 Exhaust W/Mixing Attic 23 18

H2 Exhaust W/Mixing Garage 35 29
55

Figure 36. HCHO concentration measured in the main and master zones of House 1 and House 2 

during the baseline test and four ventilation system tests

As shown in Figure 37, HCHO concentration was measured in the vented attic of House 1 and 

the unvented attic of House 2, as well as both garages during the exhaust with mixing test. The 

exhaust with mixing test was a period with somewhat higher wind than for the other test periods

(4–8 mph versus 0–2 mph) as shown in Figure 12. The vented attic concentration was about 3 

times higher than what would be expected for outdoors (~3 μg/m3

), while the unvented attic was 

about 8 times higher. The garages of House 1 and House 2 showed 25 μg/m3 and 35 μg/m3

, 

respectively.

Figure 37. Attic and garage HCHO concentrations for both houses

0

10

20

30

40

50

60

70

80

baseline exhaust exh 

w/mixing

CFIS ERV

Concentration (

μg/m3)

Formaldehyde Concentration

by Ventilation System Type

H1 Main

H1 Master

H2 Main

H2 Master

0

5

10

15

20

25

30

35

40

Attic Garage

Concentration (

μg/m3)

Formaldehyde Concentration

in Attic and Garage

H2

H1

vented

unvented
56

4.6 Volatile Organic Compound Sampling

Sampling for VOCs was done during the last 11⁄2 hour of each 24-hour test period.

Concentrations of the Top 20 VOCs were reported by the testing lab. The top half of those are 

shown in Figure 38 through Figure 41. The trend was that the baseline test showed the highest 

VOC concentrations, followed by the exhaust and exhaust with mixing ventilation systems, then 

the CFIS and ERV ventilation systems. In a few cases the order was different, and in some cases 

the results for all systems were relatively close to each other.

A full list of the functional descriptions of the VOCs found in the living zones, attics, and 

garages is given in Appendix A The highest concentrations found in House 1 were for xylene 

and benzene, solvents used in sealing the decoratively stained concrete floors throughout both 

houses. In House 2, a floor sealer was used that was designed to be lower emitting than the sealer 

used in House 1, and it apparently worked as advertised. House 2 also used a special gypsum 

board reported to absorb VOCs. Two of the top three compounds found in the House 2 unvented 

attic were related to the foam insulation used in the walls and unvented attic. Besides the xylene, 

benzene, and toluene solvents used in finishing the stained concrete floors in House 1, the 

predominant compounds found in both houses were:

• Pinene—used as a fragrance chemical

• Limonene—used in flavor, fragrance, cosmetics, and cleaning products

• Hexanal—used in flavor products

• Carene—used in flavor and fragrance products; occurs naturally in turpentine, rosemary, 

cedar, pine

• Phellandrene—used in fragrances.

Some of the same compounds found in this study were also found in a prior study by Hodgson et 

al. (2000), where in both manufactured and site-built houses, the predominant airborne 

compounds were a-pinene, HCHO, hexanal, and acetic acid.

Objectionable odor thresholds for the variety of VOCs measured in this study, many of which 

were found to be intentional fragrance or flavor products, are unknown. That was not a goal of 

this study. However, people generally know by experience about objectionable odors due to 

general living activities, often just called “stuffiness.” While even in that case constituent 

chemical odor thresholds are not known, surrogate thresholds have been found to make sense, 

such as tracking and adjusting ventilation to carbon dioxide levels when people are the 

predominant source of the odor. Controlling ventilation to avoid the “stuffiness” odor complaint 

is a practical objective in building management. The metric of annual average relative dose of 

any chemical contaminant is meaningless to this objective because the time scale is completely 

inappropriate. For general odor control, a ventilation time scale of a few hours is appropriate.

After proper local exhaust of concentrated sources, dilution of indoor odors by full distribution 

of ventilation air, and recirculation mixing to homogenize larger low concentration areas with 

smaller high concentration areas, is a practical and reasonable approach to indoor air odor 

control.
57

Figure 38. Concentrations of the top 11 VOCs found in the main zone of House 1, for the baseline

test and four different ventilation systems

Figure 39. Concentrations of the top 11 VOCs found in the master zone of House 1, for the 

baseline test and four different ventilation systems

0 20 40 60 80 100 120 140 160 180

Xylene (para and/or meta)

Xylene, ortho

Benzene, ethyl

Hexanal

3-Carene

-Phellandrene*

Cyclopentasiloxane, decamethyl

Limonene (Dipentene; 1-Methyl-4-(1-

methylethyl)cyclohexene)

Benzene, 1-methylethyl (Cumene)

Pinene, (6,6-Dimethyl-2-methylenebicyclo[3.1.1]heptane)

Nonyl aldehyde (Nonanal)

Concentration (μg/m3)

H1 baseline, Main

H1 exhaust, Main

H1 exh w/mix, Main

H1 CFIS, Main

H1 ERV, Main

0 50 100 150 200

Xylene (para and/or meta)

Xylene, ortho

Benzene, ethyl

Hexanal

3-Carene

-Phellandrene*

Cyclopentasiloxane, decamethyl

Limonene (Dipentene; 1-Methyl-4-(1-

methylethyl)cyclohexene)

Benzene, 1-methylethyl (Cumene)

Pinene, (6,6-Dimethyl-2-methylenebicyclo[3.1.1]heptane)

Nonyl aldehyde (Nonanal)

Concentration (μg/m3)

H1 baseline, Master

H1 exhaust, Master

H1 exh w/mix, Master

H1 CFIS, Master

H1 ERV, Master
58

Figure 40. Concentrations of the top 10 VOCs found in the main zone of House 2, for the baseline

test and four different ventilation systems

Figure 41. Concentrations of the top 10 VOCs found in House 2 master zone, for the baseline test 

and four different ventilation systems

0 20 40 60 80 100

Pinene, (2,6,6-Trimethylbicyclo[3.1.1]hept-2-ene)

Hexanal

Limonene (Dipentene; 1-Methyl-4-(1-

methylethyl)cyclohexene)

3-Carene

-Phellandrene*

Pinene, (6,6-Dimethyl-2-methylenebicyclo[3.1.1]heptane)

Cyclopentasiloxane, decamethyl

Pentanal

1-Pentanol (N-Pentyl alcohol)

Nonyl aldehyde (Nonanal)

Concentration (μg/m3)

H2 baseline, Main

H2 exhaust, Main

H2 exh w/mix, Main

H2 CFIS, Main

H2 ERV, Main

0 20 40 60 80 100

Pinene, (2,6,6-Trimethylbicyclo[3.1.1]hept-2-ene)

Hexanal

Limonene (Dipentene; 1-Methyl-4-(1-

methylethyl)cyclohexene)

3-Carene

-Phellandrene*

Pinene, (6,6-Dimethyl-2-methylenebicyclo[3.1.1]heptane)

Cyclopentasiloxane, decamethyl

Pentanal

1-Pentanol (N-Pentyl alcohol)

Nonyl aldehyde (Nonanal)

Concentration (μg/m3)

H2 baseline, Master

H2 exhaust, Master

H2 exh w/mix, Master

H2 CFIS, Master

H2 ERV, Master
59

Table 16 shows the VOC concentrations measured in the attics of both houses and provides a 

description of the typical functional use of each compound, as researched on the Internet. Once 

again, the solvents used in finishing the decorative concrete floors in the living space show up in 

the House 1 attic. The remaining compounds were mostly seemingly low-risk fragrance and 

flavor products. Figure 42 shows the data from Table 6 in graphical form.

Total volatile organic compound (TVOC) measurements are reported in Table 14 by house, 

zone, and ventilation system. The TVOC data showed that, compared to the exhaust system, the 

CFIS and ERV ventilation systems reduced TVOCs by 47% and 57%, respectively, averaged 

between the two houses. Compared to the baseline tests, the exhaust system increased TVOC by 

37% in the House 1 main zone, and increased TVOC by 18% in the House 2 master zone. This 

highlights that the unknown air path, or source of outside air, for the exhaust ventilation system 

can cause indoor air to be more contaminated depending on what contaminants are picked up on 

the way in.

Table 14. TVOC by House, Zone, and Ventilation System

Test

#

Ventilation

System

Main Zone Master Zone

TVOC

μg/m3

% Diff.

From

Exhaust

TVOC

μg/m3

% Diff.

From

Exhaust

Average

% Diff.

House 1

1 Baseline 690 –37% 1,310 123% 43%

2 Exhaust 1100 – 588 – –

3 Exhaust w/mixing 820 –25% 865 47% 11%

4 CFIS 459 –58% 458 –22% –40%

5 ERV 357 –68% 271 –54% –61%

House 2

1(6) Baseline 519 6% 511 –18% –6%

2 Exhaust 491 – 622 – –

3 Exhaust w/mixing 477 –3% 438 –30% –16%

4 CFIS 264 –46% 252 –59% –53%

5 ERV 295 –40% 209 –66% –53%

Combined

1 Baseline 18%

2 Exhaust –

3 Exhaust w/mixing –3%

4 CFIS –47%

5 ERV –57%

TVOC measurements in the attic and garage zones of both houses were taken at the same time 

during the exhaust with mixing test. These values are shown in Table 15. The TVOC 

measurement in the unvented attic of House 2 was slightly higher than the baseline test 

measurements in the main and master zones, and, as expected, the unvented attic of House 2 

showed higher TVOC than the vented attic of House 1. Neither of the garages had any vehicles 
60

or equipment with engines or fuel. The House 1 garage housed an atypical series of large 

batteries. 

Table 15. TVOC Measurements in the Attic and Garage Zones of Both Houses

Test

#

Ventilation

System

Attic TVOC

μg/m3

Garage TVOC

μg/m3

3 House 1

Exhaust w/mixing 200 302

3 House 2

Exhaust w/mixing 602 132

Table 17 shows the VOC concentrations measured in the garages of both houses. Once again, the 

compounds with the highest concentrations were found to be used in flavor, fragrance, 

cosmetics, and cleaning products. Figure 43 shows the data from Table 17 in graphical form.
61

Table 16. VOCs Found in Both Attics, Sorted by High to Low Concentration in the 

House 2 Unvented Attic

CAS 

Number VOC

H1-T3 

ATTIC

H2-T3 

ATTIC Functional Description

μg/m3 ppb μg/m3 ppb

3033-62-3 Ethanamine, 2,2'-

oxybis[N,N-dimethyl- 62.3 9.5 Used in 2-component polyurethane foam

66-25-1 Hexanal 16.1 3.9 46.6 11.4 Flavor products

13674-84-5 Tris(1-chloro-2-

propyl)phosphate 44.9 3.4 Flame retardant in polyurethane foams

138-86-3

Limonene (Dipentene; 1-

Methyl-4-(1-

methylethyl)cyclohexene)

7.9 1.4 37.2 6.7 Used in flavor, fragrance, cosmetics, and cleaning products

555-10-2 -Phellandrene* 7.4 1.3 34.0 6.1 Phellandrenes are used in fragrances because of their pleasing aromas

80-56-8 Pinene, (2,6,6-Trimethylbicyclo[3.1.1]hept-2-ene) 11.1 2.0 30.0 5.4 Fragrance chemical

13466-78-9 3-Carene 7.9 1.4 27.3 4.9 Flavor and fragrance products; occurs naturally in turpentine, 

rosemary, cedar, pine

127-91-3

Pinene, (6,6-Dimethyl-2-

methylenebicyclo[3.1.1]heptane)6.1 1.1 22.2 4.0 Fragrance chemical

124-19-6 Nonyl aldehyde (Nonanal) 6.6 1.1 20.7 3.6 Flavor and fragrance products.

124-13-0 Octanal 4.2 0.8 15.0 2.9 Flavor and fragrance products

71-41-0 1-Pentanol (N-Pentyl 

alcohol) 3.2 0.9 14.7 4.1 Food additive: functional use(s) - flavor and fragrance agents; also used in paper products in contact with dry food

110-62-3 Pentanal 3.7 1.1 12.0 3.4 Flavor, rubber accelerator

111-71-7 Heptanal (Heptaldehyde) 2.8 0.6 10.9 2.3 Flavor and fragrance products

111-70-6 1-Heptanol 10.9 2.3 Food additive: functional use(s) - flavor and fragrance agents

140-67-0 Estragole (4-Allylanisole) 8.2 1.4 Flavor and fragrance; distilled from basil

111-87-5 1-Octanol 7.1 1.3 Food additive: functional use(s) - flavor and fragrance agents

123-35-3 1,6-Octadiene,7-methyl-3-

methylene (Myrcene) 6.4 1.1 Fragrance chemical
62

CAS 

Number VOC

H1-T3 

ATTIC

H2-T3 

ATTIC Functional Description

μg/m3 ppb μg/m3 ppb

99-83-2 -Phellandrene* 6.1 1.1 Phellandrenes are used in fragrances because of their pleasing aromas

100-52-7 Benzaldehyde 2.1 0.5 5.9 1.4 Almond flavor

541-02-6 Cyclopentasiloxane, 

decamethyl 1.7 0.1 5.7 0.4 Cosmetics, personal-care products, manufacture of silicone polymers

106-42-3 Xylene (para and/or meta) 33.8 7.8 Solvent, paint and varnish thinner

95-47-6 Xylene, ortho 28.7 6.6 Solvent, paint and varnish thinner

100-41-4 Benzene, ethyl 6.6 1.5 Used in the production of (poly)styrene, and in some paints

3221-61-2 Octane, 2-methyl 4.3 0.7 Hydrocarbon fuel, solvent

64-19-7 Acetic acid 2.2 0.9 Vinegar, food additive; also used industrially in the production of 

wood glue, synthetic fabrics

1120-21-4 Undecane 2.1 0.3 Hydrocarbon fuel, solvent

108-88-3 Toluene (Methylbenzene) 1.9 0.5 Solvent, paint thinner; also used in adhesives and fuels
63

Figure 42. VOCs found in the attics of House 1 and House 2

0.0 20.0 40.0 60.0 80.0

Ethanamine, 2,2'-oxybis[N,N-dimethylHexanal

Tris(1-chloro-2-propyl)phosphate

Limonene (Dipentene; 1-Methyl-4-(1-methylethyl)cyclohexene)

-Phellandrene*

Pinene, (2,6,6-Trimethyl-bicyclo[3.1.1]hept-2-ene)

3-Carene

Pinene, (6,6-Dimethyl-2-methylene-bicyclo[3.1.1]heptane)

Nonyl aldehyde (Nonanal)

Octanal

1-Pentanol (N-Pentyl alcohol)

Pentanal

Heptanal (Heptaldehyde)

1-Heptanol

Estragole (4-Allylanisole)

1-Octanol

1,6-Octadiene,7-methyl-3-methylene (Myrcene)

-Phellandrene*

Benzaldehyde

Cyclopentasiloxane, decamethyl

Xylene (para and/or meta)

Xylene, ortho

Benzene, ethyl

Octane, 2-methyl

Acetic acid

Undecane

Toluene (Methylbenzene)

Concentration (μg/m3)

H1 Attic

H2 attic
64

Table 17. VOCs Found in Both Garages, Sorted by Highest to Lowest in the House 1 Garage

CAS Number VOC H1-T3 GARAGE H2-T3 GARAGE

μg/m3 ppb μg/m3 ppb

138-86-3 Limonene (Dipentene; 1-Methyl-4-(1-

methylethyl)cyclohexene) 63.5 11.4 11.6 2.1

66-25-1 Hexanal 21.0 5.1 7.9 1.9

106-42-3 Xylene (para and/or meta) 16.8 3.9

80-56-8 Pinene, (2,6,6-Trimethyl-bicyclo[3.1.1]hept-2-ene) 16.7 3.0 10.4 1.9

13466-78-9 3-Carene 15.2 2.7 10.5 1.9

555-10-2 -Phellandrene* 13.8 2.5 12.0 2.2

95-47-6 Xylene, ortho 13.6 3.1

127-91-3 Pinene, (6,6-Dimethyl-2-methylene-bicyclo[3.1.1]heptane) 11.7 2.1 6.8 1.2

124-19-6 Nonyl aldehyde (Nonanal) 9.3 1.6 4.4 0.8

29911-28-2 2-Propanol, 1-(2-butoxy-1-methylethoxy)- (Dipropylene 

glycol monobutyl ether) 6.0 0.8

71-41-0 1-Pentanol (N-Pentyl alcohol) 5.5 1.5 2.4 0.7

1120-21-4 Undecane 5.4 0.8

110-62-3 Pentanal 4.7 1.3 2.2 0.6

124-13-0 Octanal 4.2 0.8 2.3 0.4

112-40-3 Dodecane 3.4 0.5 1.7 0.2

62016-14-2 Octane, 2,5,6-trimethyl* 3.4 0.5

100-41-4 Benzene, ethyl 3.2 0.7

140-67-0 Estragole (4-Allylanisole) 3.2 0.5

111-71-7 Heptanal (Heptaldehyde) 3.1 0.7

78-93-3 2-Butanone (Methyl ethyl ketone, MEK) 3.0 1.0 1.8 0.6

111-87-5 1-Octanol 3.0 0.6

110-43-0 2-Heptanone 3.0 0.6

64-19-7 Acetic acid 6.0 2.4

78-78-4 Butane, 2-methyl (Isopentane) 3.5 1.2

109-66-0 Pentane 3.5 1.2
65

CAS Number VOC H1-T3 GARAGE H2-T3 GARAGE

μg/m3 ppb μg/m3 ppb

108-88-3 Toluene (Methylbenzene) 2.6 0.7

108-94-1 Cyclohexanone 2.5 0.6

109-99-9 Furan, tetrahydro (THF) 1.8 0.6

100-52-7 Benzaldehyde 1.6 0.4

586-62-9 Cyclohexene, 1-methyl-4-(1-methylethylidene)* 1.5 0.3

100-42-5 Styrene 1.5 0.2

*Indicates best NIST/EPAINIH library match only.
66

Figure 43. VOCs found in the garages of House 1 and House 2

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

Limonene (Dipentene; 1-Methyl-4-(1-...

Hexanal

Xylene (para and/or meta)

Pinene, (2,6,6-Trimethyl-bicyclo[3.1.1]hept-2-...

3-Carene

-Phellandrene*

Xylene, ortho

Pinene, (6,6-Dimethyl-2-methylene-...

Nonyl aldehyde (Nonanal)

2-Propanol, 1-(2-butoxy-1-methylethoxy)-...

1-Pentanol (N-Pentyl alcohol)

Undecane

Pentanal

Octanal

Dodecane

Octane, 2,5,6-trimethyl*

Benzene, ethyl

Estragole (4-Allylanisole)

Heptanal (Heptaldehyde)

2-Butanone (Methyl ethyl ketone, MEK)

1-Octanol

2-Heptanone

Acetic acid

Butane, 2-methyl (Isopentane)

Pentane

Toluene (Methylbenzene)

Cyclohexanone

Furan, tetrahydro (THF)

Benzaldehyde

Cyclohexene, 1-methyl-4-(1-methylethylidene)*

Styrene

Concentration (μg/m3)

H1 Garage

H2 Garage
67

5 Summary of Results

The research presented here was intended to develop a better understanding of whole-building 

ventilation system effectiveness and distribution in low energy homes which is critical to 

promoting the best low-energy and high-value ventilation solutions. Through this research 

project BSC sought to address the following research questions. The answers to those questions 

are provided below in the form of conclusions and recommendations:

1. Do different whole-building ventilation systems perform significantly differently in 

terms of their ability to deliver uncontaminated ventilation air to the occupants?

The testing showed that source of the single-point exhaust ventilation was not direct from outside 

(much of it came from the attic), the ventilation air was not distributed, and no provision existed 

for air filtration. Indoor air recirculation by a central air distribution system can help improve the 

exhaust ventilation system by way of air mixing and filtration. In contrast, the supply and 

balanced ventilation systems showed that there is a significant benefit to drawing outside air 

from a known outside location, and filtering and distributing that air.

In terms of internal air distribution, the baseline system showed little inter-zonal airflow in all 

cases, which confirmed that the trends indicated by the interzonal airflow results were reliable.

All systems showed little interzonal airflow between bedrooms. The most interzonal airflow was 

between the main zone and bedroom zones for the CFIS and exhaust with mixing cases. The 

Exhaust cases showed significant airflow from main to master and no airflow in the reverse 

direction, as expected with the exhaust fan located in the master zone. Otherwise, the Exhaust 

systems showed little inter-zonal airflow and distribution of ventilation air. The ERV system 

showed little airflow from Main to bedrooms and between bedrooms, but relatively high airflow 

from bedrooms to the Main zone, as expected since the ERV system supplied fresh air to the 

bedrooms and exhausted stale air from the Main zone.

2. What measurements and testing protocols are needed to appropriately account for 

the source of outside air relevant to occupant exposure to chemical and particulate 

contaminants in residential environments?

The full test battery applied in this research project was utilized to answer the research questions 

posed. The PFT testing and analysis was required to identify and compare zone air change rates 

and inter-zonal airflow which informed the ventilation air distribution question. The interzonal

airflow results also helped inform the finding of a relative average of 70% higher particle counts

in the 0.3–2.0 micron range using exhaust ventilation where a substantial amount of the 

ventilation air came across the dirty attic floor environment. The particulate, HCHO, and other 

VOC measurements taken in more than one zone supported the consistency and reliability of the 

measurement and analysis methods, and showed clear differences in the resulting indoor air 

quality between ventilation systems. Indoor and outdoor temperature and RH temperature, and 

wind speed measurements provided assurance that significant differences would not be related to 

those factors. The extensive building characterization measurements made sure that there were 

not large anomalies in building enclosure air leakage, or mechanical system operation and 

allowed for future modeling to expand the findings beyond the measured test results.
68

3. What is the overall indoor air quality impact of operating an exhaust wholebuilding ventilation system versus supply and balanced ventilation?

Exhaust ventilation testing showed lower uniformity of outdoor air exchange rate between living 

space zones, and higher concentrations of particulates, HCHO, and other Top 20 VOCs than did 

the supply and balanced ventilation systems.

4. For whole-building ventilation systems that do not draw outside air directly from a 

known fresh air source, how much of the ventilation air is drawn through 

potentially contaminated adjacent spaces such as garages and vented attics?

For the two houses studied, exhaust ventilation testing showed that only a small amount of air 

was drawn from the garage while a considerable amount was drawn from the attics, more so 

from the vented attic. The exhaust ventilation system in House 1 was moving approximately 

20% of its air ventilation air from the vented attic to the main zone. Approximately 14% of the 

exhaust ventilation air in House 1 was moving from the attic to the bedroom zones. In 

comparison, for the unvented attic of House 2, the Exhaust system moved approximately 2% of 

its ventilation air from the attic to the main zone. This indicates that the exhaust makeup air 

resistance path to outside was greater through the unvented attic than through the vented attic 

and an Exhaust ventilation system may perform better in an unvented attic house.

5. What is the impact of drawing outdoor air through the building enclosure and 

adjacent unoccupied spaces on the level of particulate contaminants within the 

conditioned space?

Drawing air through the building enclosure and adjacent spaces via exhaust ventilation showed 

approximately 70% higher concentrations of particulates on average relative to ventilation 

systems that had direct outside air intake and filtered that air. The highest particulate levels were 

found for the exhaust system, followed by the baseline or ERV, followed by the exhaust with 

mixing and CFIS. CFIS always showed the lowest particle counts regardless of particle size. This 

indicated that the filters in the central air distribution system were removing a significant amount 

of particle contaminant 0.3 micron and larger. The CFIS ventilation system showed an

approximate 85% and 73% reduction in 0.3–2.0 micron particles for House 1 and House 2, 

respectively, attributable to recirculation air filtration by operation of the central air distribution 

system. 

6. What is the impact of drawing outdoor air through the building enclosure and 

adjacent unoccupied spaces on the level of chemical contaminants within the 

conditioned space?

Drawing air through the building enclosure and adjacent spaces via exhaust ventilation showed 

higher concentrations of formaldehyde and other Top 20 VOCs.

In House 1, all ventilation systems reduced the HCHO concentration over the baseline 

concentration, which was roughly 15–20 times higher than what would be expected outdoors.

Exhaust-only ventilation reduced the indoor HCHO concentration the least, followed by exhaust 

with mixing, CFIS, and ERV. In House 2, the exhaust systems either increased or did not 

appreciably change the HCHO concentration in the main and master zones. The CFIS and ERV 
69

systems showed a significant reduction in HCHO concentration over the baseline and exhaust 

tests. In general for both houses, the CFIS and ERV systems showed a 60%–70% reduction in 

HCHO concentration over exhaust.

HCHO concentration was also measured in the attics and garages of both houses during the 

exhaust with mixing test. The vented attic concentration was about 3 times higher than what 

would be expected for outdoors, while the unvented attic and the garages were about 8–10 times 

higher.

Concentrations of the Top 20 VOCs were reported by the lab analysis. The trend found in the 

main and master zones was that the baseline test tended to show the highest VOC concentrations, 

followed by the exhaust and exhaust with mixing ventilation systems, then the CFIS and ERV 

ventilation systems. In a few cases the order was different, and in some cases the results for all 

systems were relatively close to each other.

The highest VOC concentrations found in House 1 were for xylene and benzene, solvents used in 

sealing the decoratively stained concrete floors throughout both houses. In House 2, a floor 

sealer was used that was designed to be lower emitting than the sealer used in House 1, and it 

apparently worked as advertised. House 2 also used a special gypsum board reported to absorb

VOCs. Besides the xylene, benzene, and toluene solvents used in finishing the stained concrete 

floors in House 1, the seemingly harmless balance of predominant compounds found in both 

houses were:

• Pinene—used as a fragrance chemical

• Limonene—used in flavor, fragrance, cosmetics, and cleaning products

• Hexanal—used in flavor products

• Carene—used in flavor and fragrance products; occurs naturally in turpentine, rosemary, 

cedar, pine

• Phellandrene— used in fragrances.

TVOC data showed that, compared to the exhaust system, the CFIS and ERV ventilation systems 

reduced TVOCs by approximately 47% and 57%, respectively, averaged between the two 

houses. Compared to the baseline tests, the exhaust system increased TVOC by approximately 

37% in the House 1 main zone, and increased TVOC by approximately 18% in the House 2 

master zone. This highlights that the unknown air path, or source of outside air, for the exhaust 

ventilation system can cause indoor air to be more contaminated depending on what 

contaminants are picked up on the way in.
70

6 Author Recommendations

The following thoughts and recommendations are presented by the primary author, based on the 

results of this study. This section is based on the experience of the author and does not 

necessarily reflect the recommendations of the Building America Program or DOE.

6.1 Relevant Issues With ASHRAE Standard 62.2

ASHRAE Standard 62.2-2010 may be considered to currently contain the “standard of care” for

ventilation system design and operation in residential buildings, yet some believe there are some 

technology gaps with that Standard. ASHRAE Standard 62.2 uses a catch-all approach that 

assumes that the entire house is a single, well-mixed zone and that there is no difference between 

different whole-building ventilation systems in providing effective ventilation. To try to facilitate 

that assumption, the ventilation rate has to be high enough to accommodate the worst performing 

system, which is single point exhaust. Utilizing high performing systems that draw outside air 

from a known fresh air location and filter and fully distribute that air to the occupants’ breathing 

zone (including bedrooms where occupants spend the most continuous time) should allow 

optimization of the ventilation rate to avoid the energy consumption and moisture control 

problems of overventilation.

The ventilation rates in ASHRAE Standard 62.2 are currently based on the collective engineering 

judgment of the committee members. To the knowledge of this author, there is no published 

basis for the rates in any health or medical study. Therefore, this author believes that the 

numerical recommendations established based on the results of this study are appropriate, using 

similar logic used by the ASHRAE 62.2 committee.

ASHRAE Standard 62.2 uses relative annual average dose to a generic contaminant as the metric 

to allow for a performance-based compliance approach and to account for intermittent versus 

continuous ventilation. That metric may be valid for avoiding exposure to contaminants that may 

cause cancer over 20 years, but that metric ignores shorter term odor, moisture, and sensory 

irritation effects, which is really the only obvious metric occupants have available to determine 

their satisfaction level with indoor air. While the available medical science for cancer causingchemical contaminants at concentrations typically found in residential environments is almost 

nonexistent, the science for shorter term asthma and allergy response is better known (Bornehag 

et al. 2004). Occupant observation of objectionable odor, visible moisture, or mold caused by 

that moisture, and sensory irritation is overt. Those overt objections are what home builders have 

to deal with even though ASHRAE Standard 62.2 primarily does not.

6.1.1 Source of Outside Air

ASHRAE Standard 62.2-2010 requires that supply and balanced ventilation systems draw 

outside air directly from a known fresh air location but does not include any such requirement for 

exhaust ventilation systems. Therefore, makeup air for exhaust ventilation air comes from the 

paths of least resistance, which could be through a garage, attic, crawlspace, basement, or other

soil contact location. To be consistent, at the very least the Standard would need to require 

intentional makeup air inlets, or, much better, require a supply system that provides makeup air 

from a known fresh air location whenever the whole-building exhaust ventilation system was 

operating.
71

In contrast, the following building codes have provisions requiring direct outside air for all 

ventilation systems: the International Mechanical Code (IMC), the Washington State Ventilation 

and Indoor Air Quality (WAVIAQ) Code, the U. S. Housing and Urban Development (HUD) 

Code, and the National Building Code (NBC) of Canada. A brief description of those 

requirements follows:

IMC 2012: The IMC 2012 requires a balanced ventilation system with outdoor supply air

approximately equal to exhaust air.

WAVIAQ Code 2009: The WAVIAQ Code 2009 requires that ventilation systems must 

have direct outdoor air inlets, and that they be screened and located so as not to take air 

from a list of contaminated areas, including areas where odors may be objectionable, 

attics, crawlspaces, or garages.

HUD Code 2008: The HUD Code requires that the ventilation system be balanced, and 

designed to exchange air directly with the exterior of the home. It specifically prohibits 

air drawn from the space underneath the home, through the floor, walls, or ceiling/roof 

systems.

NBC 2005: The NBC 2005 stipulates that outside air supply be provided and connected 

directly to outside.

6.1.2 Ventilation Effectiveness

In terms of ventilation effectiveness, ASHRAE Standard 62.2 accounts only for temporal (time 

based) effectiveness over an annual average; there is no provision for spatial (space-to-space) 

ventilation distribution effectiveness, or system effects. In other words, ASHRAE Standard 62.2 

accounts for ventilation effectiveness only in regards to system runtime. Even so, while the 

maximum ventilation air delivery cycle time is truncated to one day, the runtime effectiveness 

values are based on calculations that would allow the ventilation system to be off for months 

without any decrease in effectiveness, because the evaluation metric is locked to relative annual 

average exposure to a generic contaminant11. That approach ignores shorter term indoor air 

quality effects of odor and sensory irritation, which are nevertheless stated parts of an acceptable 

indoor air quality approach in the ASHRAE Standard 62.2 Scope, and definitions of “acceptable 

indoor air quality” and “air cleaning.”

In contrast, the following building codes have provisions requiring ventilation air distribution for 

all whole-building ventilation systems: IMC, Minnesota Building Code, WAVIAQ Code, the 

HUD Code, and the NBC of Canada. A brief description of those requirements follows:

IMC 2012: The IMC requires an approximately balanced ventilation system with the 

ventilation supply system designed to deliver the required rate of outdoor airflow to the 

breathing zone within each occupiable space. The WAVIAQ Code requires the 

 11 Relative annual average dose is the only metric used in ASHRAE Standard 62.2 for the performance based 

compliance method and to calculate intermittent ventilation effectiveness factors. The method tracks a generic 

contaminant (rather than any specific contaminants) and compares the annual average dose of the generic 

contaminant (in an assumed single-zone, well-mixed building model) using an actual continuous or intermittent 

ventilation air exchange rate relative to a reference continuous air exchange rate.
72

introduction and distribution of outdoor air and the removal of indoor air by mechanical 

means. It further requires that outdoor air be distributed to each habitable room by means 

such as individual inlets, separate duct systems, or a forced-air system.

MBC 2009: The MBC requires ventilation air distribution and circulation such that

outdoor air is delivered to each habitable space by a forced air circulation system, separate 

duct system, individual inlets, or a passive opening. When outside air is directly ducted to 

a forced air circulation system, circulation of 0.075 cfm/ft2 must be maintained on average 

each hour. When outside air is not directly ducted to a forced air circulation system, 

circulation of 0.15 cfm/ft2 must be maintained on average each hour (a 100% increase).

WAVIAQ Code 2009: The WAVIAQ Code requires the introduction and distribution of 

outdoor air and the removal of indoor air by mechanical means. It further requires that 

outdoor air be distributed to each habitable room by means such as individual inlets, 

separate duct systems, or a forced-air system. Conflictingly, in homes with exhaust only 

ventilation systems without outdoor air inlets the home must have a ducted forced air 

heating system that communicates with all habitable rooms and the interior doors must be 

undercut to a minimum of 1⁄2 in. above the surface of the finish floor covering; however, 

nothing is mentioned about a minimum interval of ducted forced air heating system 

communication with all habitable spaces. This will typically leave days and weeks on end 

with little or no ventilation air distribution.

HUD Code 2008: The HUD Code requires that ventilation system be designed to ensure 

that outside air is distributed to all bedrooms and main living areas.

NBC 2005: In the NBC, for ventilation systems not used in conjunction with a forced air 

heating system, an outside air supply ventilation fan is required with the same rated 

capacity as the principle [exhaust] ventilation fan to distribute outside air directly to all 

bedrooms through a system of supply ducts. Where an exhaust-only system is installed via 

the principal ventilation fan, the exhaust fan control must be wired so that activation of the 

exhaust fan automatically activates the circulation fan of the forced air distribution system 

required at its rated capacity but not less than 5 times the rated capacity of the exhaust fan.

Alternately, interlocking the forced air distribution system's circulation fan with the 

principal (exhaust) ventilation fan can be accomplished where the forced air distribution 

system is equipped with a control that automatically activates the circulation fan at userselected intervals.

ASHRAE Standard 62.2 does not attempt to address the issue of delivery of outdoor airflow to 

each space, or to the breathing zone within each occupiable space, or forced air 

circulation/distribution of ventilation air. It simply makes an overreaching assumption that for all 

ventilation system cases, the entire house is a single, well-mixed zone, focusing only on relative 

annual average exposure.

6.2 Recommendations for Ventilation Rates

Exhaust ventilation testing showed lower uniformity of outdoor air exchange rate between living 

space zones, and higher concentrations of particulates, HCHO, and other Top 20 VOCs than did 

the supply and balanced ventilation systems. This showed that single-point exhaust ventilation 
73

was inferior as a whole-house ventilation strategy. It was inferior because the source of outside 

air was not direct from outside (much of it came from the attic), the ventilation air was not 

distributed, and no provision existed for air filtration. Indoor air recirculation by a central air 

distribution system can help improve the exhaust ventilation system by way of air mixing and 

filtration. In contrast, the supply and balanced ventilation systems showed that there is a 

significant benefit to drawing outside air from a known outside location, and filtering and 

distributing that air.

ASHRAE Standard 62.2 has set a ventilation airflow rate method that does not differentiate 

between better and worse performing whole-building ventilation systems. The rates set are 

inferred to be adequate for the worst performing system. System factors as shown in Table 18

could be applied to allow accounting for ventilation system attributes that improve a system’s 

performance. The system factors are based on engineering judgment resulting from this study 

and previous studies (Hendron et al. 2006, 2007; Rudd and Lstiburek 2000, 2001, 2008; 

Townsend et al. 2009a, 2009b), and extensive work with the ASHRAE Standard 62.2 committee 

on this subject since 2006. Engineering judgment is valid here since the ASHRAE Standard 62.2 

ventilation rates are themselves based only on the engineering judgment and experience of the 

committee members, not on any health or medical studies. In terms of multizone ventilation air 

change effectiveness, the cited previous research found that fully distributed supply ventilation, 

operating at half the airflow of single-point exhaust, uniformly ventilated all spaces to a level 

that equaled or exceeded the ventilation level of the lesser ventilated spaces using the exhaust 

system. This study added new elements of ventilation effectiveness research, accounting for 

source of outside air, particle contaminants, and VOC contaminants. These new data give further 

support for ventilation rate credit for better performing ventilation systems, such as supply and 

balanced ventilation compared to exhaust, and systems with predictable filtration of outside air 

and recirculation filtration. The Table 18 System Factors are recommended for consideration in 

the Building America program (including the DOE Challenge Home) to allow credit for better 

performing ventilation systems. This would yield energy savings and reduced moisture control 

risk in humid climates, without compromising indoor air quality relative to the worst performing 

system allowed by ASHRAE Standard 62.2.

Table 18. Recommended System Factors To Reduce Ventilation Fan 

Airflow Rates Relative to ASHRAE Standard 62.2-2013

Mechanical Ventilation 

System Type

With Central Filtration 

Recirculation*

Without Central 

Filtration Recirculation

Balanced 0.5 0.7

Unbalanced Supply 0.55 0.75

Unbalanced Exhaust 0.7 1.0

* Requires minimum whole-house recirculation turnover of 0.7 ach with minimum MPR 700 or MERV 9 filter. 

Minimum whole-house recirculation turnover defined as: (AHU cfm)(minimum runtime min/h) / (conditioned floor 

area*8 ft).

The numerical basis for the system factors shown inTable 18 is given in Table 19. The values 

shown in Table 19 are percentage reductions, based on engineering judgment from this and 

previous studies, for each system improvement that exists for a given ventilation system based 

on the four System Factor Categories of Balance, Distribution, Outdoor Air Source, and 
74

Recirculation Filtration. Balance is where the mechanical ventilation system supplies to the 

house substantially the same amount of air that it exhausts from the house. That generally 

increases total air exchange somewhat since, with balanced ventilation, mechanical ventilation 

mostly sums with natural infiltration. Distribution is where direct outside air is supplied to at 

least all of the bedrooms, where occupants typically spend the most continuous time. Outdoor 

Air Source is where outside air comes directly from a known fresh air source, not drawn through 

potentially contaminated building enclosure elements or adjacent spaces such as garages, attics, 

and crawlspaces. Recirculation Filtration is where a mechanical system, such as a central heating 

and cooling system, recirculates a minimum of 70% of the house air volume each hour through 

an air filter with minimum MPR 700 or MERV 9. The Recirculation Filtration category is given 

the highest weight in light of recent determinations that particulate contamination presents by far 

(10 times more than the next closest risk) the greatest risk to human health in residential indoor 

environments (Logue et al. 2011). Referring again toTable 19, as an example, a Balanced-type 

ventilation system with whole-building recirculation filtration earns ventilation airflow reduction 

credit in all four system factor categories. An Unbalanced Exhaust-type ventilation system 

without whole-building recirculation filtration earns no ventilation airflow reduction credits.
75

Table 19. Numerical Basis for the System Factors Shown in Table 18, 

Given as Percent Airflow Rate Reduction for Each System Factor Category

Whole-Building Mechanical 

Ventilation System Type

Percent Reduction in 62.2-2013 Ventilation Rate

Due to Listed System Factor Categories

With Whole-Building Recirculation Filtration Without Whole-Building Recirculation Filtration

System Factor Categories System Factor Categories

Balance Distribution OA 

Source

Recirculation

Filtration Total Balance Distribution OA Source

Recirculation

Filtration Total

Balanced 5 10 15 20 50 5 10 15 0 30

Unbalanced Supply 0 10 15 20 45 0 10 15 0 25

Unbalanced Exhaust 0 10 0 20 30 0 0 0 0 0
76

References

ASHRAE (2010).Ventilation and Acceptable Indoor Air Quality in Low-rise Residential 

Buildings. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning 

Engineers.

ASHRAE (2013).Ventilation and Acceptable Indoor Air Quality in Low-rise Residential 

Buildings. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning 

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Children and Phthalates in House Dust: A Nested Case–Control Study.” Environmental Health 

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Flow Rates in Residences in Boston, Massachusetts.” Atmospheric Environment 41(2007):

3722–3727.

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78

Appendix A: Listing of All Top 20 Volatile Organic Compounds 

Found, and Their Functional Descriptions
79

Table 20. Listing of All Top 20 Volatile Organic Compounds Found, and Their Functional Descriptions

CAS 

Number VOC Functional Descriptions Source

99-83-2 -Phellandrene* Phellandrenes are used in fragrances because of their pleasing aromas. Wikipedia

555-10-2 -Phellandrene*

5794-03-6 (+)-Camphene Fragrance chemical.

107-21-1 1,2-Ethanediol (Ethylene glycol)

Ethylene glycol is an organic compound widely used as an automotive antifreeze 

and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, 

sweet-tasting liquid. Ethylene glycol is toxic, and ingestion can result in death.

123-35-3 1,6-Octadiene,7-methyl-3-

methylene (Myrcene) Fragrance chemical.

71-36-3 1-Butanol (N-Butyl alcohol)

Present in many foods and beverages. It is also a permitted artificial flavorant in 

the United States, used in butter, cream, fruit, rum, whiskey, ice cream and ices, 

candy, baked goods and cordials. It is also used in a wide range of consumer 

products.

Wikipedia

111-70-6 1-Heptanol Food additive: functional use(s) - flavor and fragrance agents.

111-87-5 1-Octanol Food additive: functional use(s) - flavor and fragrance agents.

71-41-0 1-Pentanol (N-Pentyl alcohol) Food additive: functional use(s) - flavor and fragrance agents. Also used in paper 

products in contact with dry food.

78-93-3 2-Butanone (Methyl ethyl ketone, 

MEK)

Used in products such as lacquer, varnishes, paint remover, a denaturing agent 

for denatured alcohol, glues, and as a cleaning agent. Wikipedia

110-43-0 2-Heptanone

Listed by the FDA as a "food additive permitted for direct addition to food for 

human consumption." It occurs naturally in certain foods such as beer, white 

bread, butter, various cheeses and potato chips.

Wikipedia

2548-87-0 2-Octenal, (E)* Food and perfume additive; can also result from oxidation of cooked food.

http://en.wikipedia.org/wiki/Warme

d-over_flavor 

http://www.flavornet.org/info/2548-

87-0.html

29911-28-2

2-Propanol, 1-(2-butoxy-1-

methylethoxy)- (Dipropylene 

glycol monobutyl ether)

Uses include: 1) coupling agent used as a blending facilitator for cleaners such as 

degreasers, paint removers, metal cleaners and hard surface cleaners; 2) coalescent 

for lowering the minimal film forming temperature in latex coatings; 3) solvent for 

water-reducible coatings; 4) chemical intermediate for production of epoxides, 

acid ester derivatives, solvents, and plasticizers.

www.arb.ca.gov/consprod/regact/20

10ra/dpnb29911282.pdf

20324-32-7 2-Propanol, 1-(2-methoxy-1-

methylethoxy)*

Used in the manufacture of a wide variety of industrial and commercial products, 

including paints, varnishes, inks, and cleaners.

OECD SIDS

DIPROPYLENE GLYCOL 

METHYL ETHER

5131-66-8 2-Propanol, 1-butoxy

A colorless combustible liquid with an ether-like odor. It has low water solubility 

and good coupling and demonstrates good solvency for coating resins. Used in 

agricultural, coating, cleaning, ink, textile and adhesive products, and as substitute 

for ethylene glycol ethers.

www.lyondellbasell.com/techlit/tech

lit/2395.pdf
80

CAS 

Number VOC Functional Descriptions Source

13466-78-9 3-Carene Flavor and fragrance products; occurs naturally in turpentine, rosemary, cedar, 

pine. Wikipedia

123-86-4 Acetate, butyl

Found in many types of fruit, where along with other chemicals it imparts 

characteristic flavors and has a sweet smell of banana or apple. It is used as a 

synthetic fruit flavoring in foods such as candy, ice cream, cheeses, and baked 

goods. Also used in the production of lacquers.

Wikipedia

64-19-7 Acetic acid Vinegar, food additive. Also used industrially in the production of wood glue, 

synthetic fabrics. Wikipedia

100-52-7 Benzaldehyde Benzaldehyde occurs in almonds, apricots, apples, and cherry kernels. It is an 

almond flavorant, and is also used as bee repellant. Wikipedia

98-82-8 Benzene, 1-methylethyl (Cumene)

Used as a thinner for paints, lacquers, and enamels and as a component of high 

octane fuels. The most probable route of human exposure is by the inhalation of 

contaminated air from the evaporation of petroleum products.

http://www.epa.gov/ttnatw01/hlthef/

cumene.html

100-41-4 Benzene, ethyl Used in the production of (poly)styrene, and in some paints. Wikipedia

78-78-4 Butane, 2-methyl (Isopentane) Used in toothpaste, cosmetics, body washes. http://www.wisegeek.com/what-isisopentane.htm, Wikipedia

108-94-1 Cyclohexanone Feedstock for production of nylon.

540-97-6 Cyclohexasiloxane, dodecamethyl Feedstock for silicone plastics. Silicone plastics have many applications; cosmetics 

and toiletries probably dominate human exposure.

oehha.ca.gov/multimedia/biomon/pd

f/1208cyclosiloxanes.pdf

586-62-9 Cyclohexene, 1-methyl-4-(1-

methylethylidene)* Flavor and fragrance; scent of pine. http://www.flavornet.org/info/586-62-9.html

541-02-6 Cyclopentasiloxane, decamethyl Cosmetics, toiletries, dry-cleaning. oehha.ca.gov/multimedia/biomon/pd

f/1208cyclosiloxanes.pdf

556-67-2 Cyclotetrasiloxane, octamethyl Cosmetics, personal-care products, manufacture of silicone polymers. oehha.ca.gov/multimedia/biomon/pd

f/1208cyclosiloxanes.pdf

112-40-3 Dodecane Hydrocarbon fuel, solvent. Wikipedia

109-99-9 Furan, tetrahydro (THF) Solvent for PVC; used in varnishes; feedstock for spandex and similar materials. Wikipedia

140-67-0 Estragole (4-Allylanisole) Flavor and fragrance; distilled from basil. Wikipedia

3033-62-3 Ethanamine, 2,2'-oxybis[N,Ndimethyl- Used in 2-component polyurethane foam.

111-90-0

Ethanol, 2-(2-ethoxyethoxy) 

(Diethylene glycol monoethyl 

ether)

Solvent in paint and wood finishes. It is included in wood stains, stamping inks, 

leather dyes, printing inks and pastes.

German Wikipedia, Google 

Translate

111-76-2 Ethanol, 2-butoxy

A solvent in paints and surface coatings, as well as cleaning products and inks. 

Used in acrylic resin formulations, asphalt release agents, firefighting foam, 

leather protectors, oil spill dispersants, degreaser applications, and photographic 

strip solutions. Used as a primary ingredient include some whiteboard cleaners, 

liquid soaps, cosmetics, dry cleaning solutions, lacquers, varnishes, herbicides, and 

latex paints. Frequently found in popular cleaning products. It is the main 

ingredient of many home, commercial and industrial cleaning solutions

Wikipedia
81

CAS 

Number VOC Functional Descriptions Source

111-71-7 Heptanal (Heptaldehyde) Flavor and fragrance products. Wikipedia

142-82-5 Heptane

Used in paints and coatings, used as the rubber cement solvent “Bestine,” used as 

the outdoor stove fuel “Powerfuel” by Primus, used as pure n-Heptane for research 

and development and pharmaceutical manufacturing and as a minor component of 

gasoline.

Wikipedia

66-25-1 Hexanal Flavor products. Wikipedia

589-34-4 Hexane, 3-methyl Hydrocarbon fuel, solvent. Wikipedia

138-86-3 Limonene (Dipentene; 1-Methyl4-(1-methylethyl)cyclohexene) Used in flavor, fragrance, cosmetics, and cleaning products. Wikipedia

111-84-2 Nonane Hydrocarbon fuel, solvent. Wikipedia

124-19-6 Nonyl aldehyde (Nonanal) Flavor and fragrance products. Wikipedia

124-13-0 Octanal Flavor and fragrance products. Wikipedia

62016-14-2 Octane, 2,5,6-trimethyl* Hydrocarbon fuel, solvent. Wikipedia

3221-61-2 Octane, 2-methyl Hydrocarbon fuel, solvent. Wikipedia

110-62-3 Pentanal Flavor, rubber accelerator. Wikipedia

109-66-0 Pentane Hydrocarbon fuel, solvent. Blowing agent for polystyrene foams. Wikipedia

80-56-8 Pinene, (2,6,6-Trimethylbicyclo[3.1.1]hept-2-ene) Fragrance chemical. Wikipedia

127-91-3 Pinene, (6,6-Dimethyl-2-

methylene-bicyclo[3.1.1]heptane) Fragrance chemical. Wikipedia

629-59-4 Tetradecane Hydrocarbon fuel, solvent. Wikipedia

100-42-5 Styrene Plastic monomer. Wikipedia

108-88-3 Toluene (Methylbenzene) Solvent, paint thinner. Also used in adhesives and fuels. Wikipedia

13674-84-5 Tris(1-chloro-2-propyl)phosphate Flame retardant in polyurethane foams. www.inchem.org/documents/sids/si

ds/13674845.pdf

1120-21-4 Undecane Hydrocarbon fuel, solvent. Wikipedia

106-42-3 Xylene (para and/or meta) Solvent, paint and varnish thinner. Wikipedia

95-47-6 Xylene, ortho Solvent, paint and varnish thinner. Wikipedia
82

Appendix B: Preliminary CONTAM Model

CONTAM (Walton and Dols 2010) is a multizone indoor air quality and ventilation analysis 

computer program designed help determine: (a) airflows in building systems driven by 

mechanical and natural means; (b) contaminant concentrations transported by these airflows; and 

(c) personal exposure of occupants to airborne contaminants. In future work, further analysis 

using the CONTAM model started in this project would allow expansion of this work for 

evaluating ventilation system impacts over a year-long period, and for different climates. A fully 

developed model could be calibrated using the tracer gas airflow results, then used to expand the

capability to further explore the source of outside air and ventilation air distribution effects over 

a broader range of conditions, such as: different seasons, climates, enclosure leakage rates, 

ventilation systems, ventilation control strategies, and air filtration/air cleaning strategies.

B.1 Building and Zonal Leakage Characterization by Fan Pressurization Testing 

Detailed whole-building and zonal leakage fan pressurization test results, including those from 

numerous guarded tests are given in Table 21 for House 1 and Table 22 for House 2. Leakage to 

outside was measured by means of a guarded test on each room/zone. Guarding the test zone was 

accomplished by using one or two more calibrated fans, and combinations of door opening, to 

take the pressure of the adjacent zones to the same pressure with respect to outside as the test 

zone. Total leakage of each zone was measured by exposing all bordering spaces to outdoors. 

Leakage to inside was calculated as the difference between total leakage and leakage to outside 

for each zone. The multi-point tests were conducted at pressures between –15 and –50 Pa with 

respect to outside, enabling determination of a flow exponent and constant from a power-law 

curve fit to predict flows at different pressures and for modeling.
83

Table 21. House 1 Guarded and Unguarded Fan Pressurization Test Results

Power Law Fit

Coefficients

Airflow at Listed Test Pressure Differential 

(CFM)

C n 15 25 30 40 50

Total Leakage

House 66.2 0.706 448 642 731 895 1048

House + Garage 110.0 0.625 598 822 922 1103 1268

Garage 31.7 0.661 190 266 300 363 421

Master 27.8 0.622 150 206 231 276 317

Middle 8.2 0.639 46 64 72 87 100

Bath 2 4.7 0.612 25 34 38 45 52

Front 10.4 0.615 55 75 84 101 115

Leakage to Outside

Master 13.3 0.693 87 124 140 171 200

Middle 2.5 0.824 23 36 41 52 63

Bath 2 Below measurable 

limit

Front 6.6 0.677 42 59 66 81 94

House to Out 56.9 0.727 407 590 674 830 977

Main to Out 34.8 0.737 255 372 426 526 620

Garage to Out 25.0 0.686 160 227 258 314 366

Leakage to Inside

Master 15.7 0.514 63 82 90 105 117

Middle 7.9 0.397 23 28 30 34 37

Bath 2 4.7 0.612 25 34 38 45 52

Front 4.7 0.390 14 17 18 20 22

Interzonal Leakage

Garage to Main 7.4 0.511 30 39 42 49 55
84

Table 22. House 2 (Unvented Attic) Guarded and Unguarded Fan Pressurization Test Results

Power Law Fit

Coefficients

Airflow (CFM) at Listed Test Pressure 

Differential

C n 15 25 30 40 50

Total Leakage

House + Attic 67.1 0.630 370 510 572 686 789

House + Attic + 

Garage 83.0 0.667 505 710 802 972 1128

House 136.8 0.613 719 984 1100 1313 1505

Attic 164.5 0.550 729 966 1068 1251 1414

Garage 62.2 0.639 351 486 547 657 758

Master 33.3 0.598 168 228 255 302 345

Middle 38.2 0.560 174 232 257 301 342

Bath 2 4.8 0.610 25 34 38 46 52

Front 13.8 0.590 68 92 103 122 139

Leakage to Outside

Master 4.5 0.540 19 25 28 33 37

Middle 0.2 1.000 3 6 7 9 11

Bath 2 Below measurable 

limit

Front 0.3 0.976 4 6 8 10 13

Attic to Out 105.6 0.558 479 636 705 827 937

Garage to Out 50.7 0.671 312 440 497 603 700

House to Out 68.8 0.677 430 608 688 836 972

Main to Out 64.7 0.676 404 570 645 783 911

Leakage to Inside

Master 28.9 0.605 149 203 226 269 308

Middle 38.7 0.549 171 227 250 293 331

Bath 2 4.8 0.610 25 34 38 46 52

Front 14.1 0.560 64 86 95 111 126

Interzonal Leakage

Attic to House 59.0 0.534 251 329 363 423 477

Garage to Main 16.2 0.327 39 46 49 54 58

The guarded tests on House 2 were particularly challenging because of the strong interzonal

airflow between the house and the unvented attic. Small differences in pressure between the 

house and attic corresponded to large airflows between the two spaces. The solution was to use 

more automation in the testing via the cruise control built into some digital manometers and 

computer software for blower door testing. The guarded testing in House 2 required three fans—

one for the room under test, one for the house front door, and one for the unvented attic. One is 

manually driven to the chosen pressure relative to outside, while the other two zones are matched 

to that pressure under computer control. A further challenge came from the very low leakage to 

outside in the secondary bedrooms and hall bathroom, once the attic leakage was eliminated by 
85

guarding. At the standard test pressures of 15–50 Pa, the leakage was below measurable limits.

Test results were recorded at flows between 20 and 50 CFM, with pressures as high as 150 Pa.

The power law flow coefficients were fit from the measured data.

B.2 Leakage Inputs for CONTAM Modeling

A preliminary CONTAM model was constructed for each of the houses using the physical 

characteristics, and the measured air leakage and mechanical airflow characteristics. The 

CONTAM model of the house includes leaks only between physically adjacent zones. For the six

zones in House 1 (where the attic is taken to be outside), this reduces the total number of 

modeled leaks from 21 to 11. However, with each room being adjacent to two or more others, the

guarded tests of total leakage to inside do not uniquely determine the path of measured leakage

area to inside. We initially planned that the leakage to inside for each subject room could be 

distributed proportionally relative to interior wall area, but analysis of the measurements showed 

that a second weighting may be needed to account for the fact that adjacent rooms can have very 

different total leakage to inside, biasing the direction of airflow from the subject room.

Therefore, initial leakage areas were chosen to limit leakage to be consistent with all the airflow 

measurements (i.e. more air could not flow in than could flow out). These are estimates, to be 

refined when the CONTAM model can be fit to the tracer gas measurements. Table 23 and Table 

24 show the initial leakage flow coefficients for the CONTAM model. Doors are entered 

separately, according to their known area.

Table 23. House 1 CONTAM Model Inputs

Leakage Path Power Law Coefficients

From To C n

Main Out 34.8 0.737

Main Master 14.8 0.514

Main Middle 0.1 0.500

Main Garage 7.4 0.511

Master Out 13.3 0.693

Master Middle 0.9 0.514

Middle Out 2.5 0.824

Middle Bath 6.3 0.500

Bath Front 2.0 0.612

Front Out 6.6 0.677

Garage Out 25.0 0.686
86

Table 24. House 2 CONTAM Model Inputs

Leakage Path Power Law Coefficients

From To C n

Main Out 64.7 0.676

Main Master 15.2 0.6

Main Middle 18.6 0.5

Main Garage 16.2 0.327

Master Out 4.5 0.54

Master Middle 13.7 0.6

Middle Out 0.22 1.0

Middle Bath 2.40 0.61

Bath Front 2.40 0.61

Front Out 0.28 0.976

Front Main 11.2 0.560

Garage Out 50.7 0.671

Attic Out 105.6 0.558

Attic Main 30.0 0.534

Attic Master 13.5 0.534

Attic Middle 6.4 0.534

Attic Bath 2.6 0.534

Attic Front 6.6 0.534

Figure 44 and Figure 45 show screenshots of the CONTAM interface, showing airflow between 

each zone and the outside when no wind is included. In future work, the model will be run to 

simulate each of the PFT tests conducted, and the modeled concentrations of gas compared to 

those which actually occurred.

Figure 44 CONTAM Model of House 1 Figure 45. CONTAM Model of House 2
87

Specific leakage locations were not defined within each room, rather, diffuse leakage is assumed, 

but defined leak heights are required for calculating stack-driven flows. For each pair of adjacent 

zones, the leakage area was divided among five modeled leaks, spaced 2 feet apart vertically.

This permits simultaneous bi-directional airflow between the zones. Townsend (2009a, b) found 

that five leaks spaced this way in CONTAM approximate the condition of diffuse leakage. Under 

this assumption, the leakage areas in each room are symmetric about the neutral pressure plane.

Therefore stack effect does not drive airflow between interior zones. The House 2 unvented attic 

is modeled, but not fully shown in Figure 45. Showing a summertime example condition, the 

unvented attic model shows outdoor temperatures warmer than indoor, when unvented attic 

airflow will be driven by stack effect infiltration into the attic and exfiltration from each 

occupied zone. The measured HVAC airflows will define the mechanically induced airflows.

Weather data will be input to the model for boundary conditions.

B.3 Future Model Refinement

The six tracer gasses used in the testing were input to CONTAM as separate contaminants. The 

time-dependent concentration of each tracer in each zone is calculated by CONTAM. The 

average concentration of each tracer as measured by the PFT samplers is calculated from these 

values in postprocessing.

As discussed previously, the fan pressurization testing did not directly measure every partition 

leakage area. Interior leakage of the bathroom and each bedroom was disaggregated for 

modeling. For this reason, and due to the limitations of fan pressurization testing for very low 

airflows, the initial leakage coefficients in the model are not expected to accurately reproduce the 

results of PFT testing. To improve the predictive value of the model, these uncertain leakage 

parameters will be adjusted. CONTAM will be called iteratively by a non-linear search 

algorithm, with the error between modeled and measured results being calculated after each run, 

and the input parameters improved.

Using all data for calibration would risk overfitting; that is, finding a model which only matches 

reality for the limited inputs used in calibration. Instead, some test data will be used in model 

refinement, and the rest used to check the model. The methodology of ASTM D5157-97 will be 

used to assess the predictions of the model.
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